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Field Identifiable Subspecies of birds – an annotated list

Below is a draft list of Field Identifiable subspecies of North American birds. Some discussion of the concept behind the list is here. Any suggestions are welcome in the comments section below. Work on the list is ongoing, and if you want to read even more “behind-the-scenes” stuff there is a discussion at BirdforumΒ here.

* Red asterisk indicates species that qualify for my subjective and arbitrary judgement as the forms most likely to be split. I have added this mainly as a way to highlight the most distinctive subspecies. Feel free to suggest changes.

Family Anatidae – Swans, Geese and Ducks

Black-bellied Whistling-Duck – Dendrocygna autumnalis

Fulvous Whistling-Duck – Dendrocygna bicolor

Taiga Bean-Goose – Anser fabalis

Tundra Bean-Goose – Anser serrirostris

Pink-footed Goose – Anser brachyrhynchus

Greater White-fronted Goose – Anser albifrons

Greenland form is fairly distinctive and usually reliably identified in the field, other forms less distinctive, intergrading, and not reliably identified out of range. ––Read more…

Greater White-fronted Goose (Greenland) – Anser albifrons flavirostris

Greater White-fronted Goose (American) – Anser albifrons gambeli group

Lesser White-fronted Goose – Anser erythropus

Greylag Goose – Anser anser

Emperor Goose – Chen canagica

Snow Goose – Chen caerulescens

Two subspecies are distinguished by overall size, but there is considerable overlap and identifying an individual out of range usually cannot be done with a high degree of confidence.

Snow Goose (Lesser) – Chen caerulescens caerulescens

Snow Goose (Greater) – Chen caerulescens atlantica

Ross’s Goose – Chen rossii

Brant – Branta bernicla

Three named subspecies recorded in North America, including five distinct populations. Several can be identified in the field with a high level of confidence. Intergrades are rare but greatly complicate identification.

Brant (Dark-bellied or Eurasian) – Branta bernicla bernicla

Brant (Pale-bellied or Atlantic) – Branta bernicla hrota

Brant (Black or Pacific) – Branta bernicla nigricans

Brant (Western High Arctic or Gray-bellied) – Branta bernicla ? subspecies unassigned

Barnacle Goose – Branta leucopsis

Cackling Goose – Branta hutchinsii

Four subspecies fall into two groups, “Pacific” minima and Aleutian subspecies can be distinguished from each other and together form a group breeding in western Alaska. Subspecies hutchinsii and taverneri nest in northern Alaska and arctic Canada; cannot be distinguished from each other but together are distinguishable from Pacific forms. ––Read more…

Cackling Goose (Pacific) – Branta hutchinsii minima *

Cackling Goose (Aleutian) – Branta hutchinsii leucopareia

Cackling Goose (Richardson’s) – Branta hutchinsii hutchinsii group *

Canada Goose – Branta canadensis

Seven subspecies, but there is so much variation and overlap that, while it is possible to pick out individuals and flocks that show the characteristics of one subspecies, these may not be safely identifiable out of range. The groups listed here can be identified with some confidence under the right circumstances. ––Read more…

Canada Goose (Dusky) – Branta canadensis occidentalis group

Canada Goose (Typical) – Branta canadensis canadensis group

Canada Goose (Lesser) – Branta canadensis parvipes

Mute Swan – Cygnus olor

Trumpeter Swan – Cygnus buccinator

Tundra Swan – Cygnus columbianus

Two subspecies distinguished by extent of yellow on bill. Virtually all individuals can be identified, with little overlap, and several authorities currently split these into two species, but no known differences in voice, behavior, or structure.

Tundra Swan (Whistling) – Cygnus columbianus columbianus

Tundra Swan (Bewick’s) – Cygnus columbianus bewickii

Whooper Swan – Cygnus cygnus

Muscovy Duck – Cairina moschata

Wood Duck – Aix sponsa

Gadwall – Anas strepera

Falcated Duck – Anas falcata

Eurasian Wigeon – Anas penelope

American Wigeon – Anas americana

American Black Duck – Anas rubripes

Mallard – Anas platyrhynchos

Mexican Mallard is nearly 100% identifable and is split by several authorities, extent of intergradation with Northern Mallard is debated.

Mallard (Northern) – Anas platyrhynchos platyrhynchos group *

Mallard (Mexican) – Anas platyrhynchos diazi *

Mottled Duck – Anas fulvigula

Florida and Gulf Coast populations differ significantly in DNA, slightly and on average in plumage. It is doubtful that they could be confidently identified in the field, but more study is warranted.

Eastern Spot-billed Duck – Anas zonorhyncha

Blue-winged Teal – Anas discors

Cinnamon Teal – Anas cyanoptera

Northern Shoveler – Anas clypeata

White-cheeked Pintail – Anas bahamensis

Northern Pintail – Anas acuta

Garganey – Anas querquedula

Baikal Teal – Anas formosa

Green-winged Teal – Anas crecca

Two subspecies easily distinguished in adult male plumage and differ significantly in DNA, split by many authorities, but no consistent differences in other plumages, voice, structure, or behavior,

Green-winged Teal (Common or Eurasian) – Anas crecca crecca group

Green-winged Teal (American) – Anas crecca carolinensis

Canvasback – Aythya valisineria

Redhead – Aythya americana

Common Pochard – Aythya ferina

Ring-necked Duck – Aythya collaris

Tufted Duck – Aythya fuligula

Greater Scaup – Aythya marila

Lesser Scaup – Aythya affinis

Steller’s Eider – Polysticta stelleri

Spectacled Eider – Somateria fischeri

King Eider – Somateria spectabilis

Common Eider – Somateria mollissima

Four subspecies in North America and two additional in Europe. The West Arctic form is the most distinctive, differing in plumage, size, and bill structure, and seems a good candidate for splitting. The three eastern North American forms are more similar to each other, with overlap in many features and intergrades where ranges meet, but many or most are still identifiable.

Common Eider (Pacific) – Somateria mollissima v-nigra *

Common Eider (Maritime Canada) – Somateria mollissima dresseri

Common Eider (East Arctic) – Somateria mollissima borealis

Common Eider (Hudson Bay) – Somateria mollissima sedentaria

Harlequin Duck – Histrionicus histrionicus

Labrador Duck – Camptorhynchus labradorius

Surf Scoter – Melanitta perspicillata

White-winged Scoter – Melanitta fusca

Adult males of Siberian subspecies (recorded a few times in western Alaska) are safely distinguishable from American subspecies.

White-winged Scoter (Stejneger’s or Siberian) – Melanitta fusca stejnegeri

White-winged Scoter (American) – Melanitta fusca deglandi

Black Scoter – Melanitta americana

Long-tailed Duck – Clangula hyemalis

Bufflehead – Bucephala albeola

Common Goldeneye – Bucephala clangula

Eurasian subspecies recorded at least once in Alaska differs slightly in size and proportions, and might just be identifiable. More study is needed.

Barrow’s Goldeneye – Bucephala islandica

Smew – Mergellus albellus

Hooded Merganser – Lophodytes cucullatus

Common Merganser – Mergus merganser

Eurasian subspecies known as Goosander (rare but regular in western Alaska) is safely distinguishable from American subspecies by wing pattern and probably by bill and head shape.

Common Merganser (Goosander or Eurasian) – Mergus merganser merganser group *

Common Merganser (American) – Mergus merganser americanus *

Red-breasted Merganser – Mergus serrator

Masked Duck – Nomonyx dominicus

Ruddy Duck – Oxyura jamaicensis

Family Cracidae – Chachalacas and Guans

Plain Chachalaca – Ortalis vetula

Family Odontophoridae – New World Quail

Mountain Quail – Oreortyx pictus

Scaled Quail – Callipepla squamata

Birds in southern Texas are browner overall, and males have a chestnut belly patch lacking in others, which probaby allows reliable identification, but more study is needed to assess variation.

California Quail – Callipepla californica

Gambel’s Quail – Callipepla gambelii

Northern Bobwhite – Colinus virginianus

Variation in Northern Bobwhite across eastern North America is subtle and clinal, and natural variations are now swamped by many released birds. Masked Bobwhite of southwest is very distinctive, males 100% identifiable by plumage (but only by plumage), females are virtually identical to Eastern birds.

Northern Bobwhite (Eastern) – Colinus virginianus virginianus group *

Northern Bobwhite (Masked) – Colinus virginianus ridgwayi *

Montezuma Quail – Cyrtonyx montezumae

Family Phasianidae – Grouse and Pheasants

Chukar – Alectoris chukar

Himalayan Snowcock – Tetraogallus himalayensis

Gray Partridge – Perdix perdix

Ring-necked Pheasant – Phasianus colchicus

Across its wide native range this species occurs in five identifiable forms. Most distinctive is the Green Pheasant of Japan, split by many authorities and introduced locally in the US. Populations in North America are derived from at least three of the other four forms, but extensive mixing of captive bred stock makes subspecies ID here essentially impossible.

Ruffed Grouse – Bonasa umbellus

Greater Sage-Grouse – Centrocercus urophasianus

Gunnison Sage-Grouse – Centrocercus minimus

Spruce Grouse – Falcipennis canadensis

Two subspecies groups differ in male plumage and display and are good candidates for species status. Females are probably indistinguishable.

Spruce Grouse (Taiga) – Falcipennis canadensis canadensis group *

Spruce Grouse (Franklin’s or Pacific) – Falcipennis canadensis franklinii group *

Willow Ptarmigan – Lagopus lagopus

Recent DNA studies indicate several distinct populations in North America. More study needed to determine whether any are identifiable in the field.

Rock Ptarmigan – Lagopus muta

Several distinctive populations in the Aleutian Islands and elsewhere differ in plumage and possibly display, more study is needed.

White-tailed Ptarmigan – Lagopus leucura

Dusky Grouse – Dendragapus obscurus

Sooty Grouse – Dendragapus fuliginosus

Sharp-tailed Grouse – Tympanuchus phasianellus

Greater Prairie-Chicken – Tympanuchus cupido

Texas (Atwater’s) subspecies differs slightly but reliably in size and plumage. The Heath Hen T. c. cupido was relatively distinctive but now extinct.

Greater Prairie-Chicken (Northern) – Tympanuchus cupido pinnatus

Greater Prairie-Chicken (Texas or Attwater’s) – Tympanuchus cupido attwateri

Lesser Prairie-Chicken – Tympanuchus pallidicinctus

Wild Turkey – Meleagris gallopavo

Southwestern birds differ in plumage, but similar birds can be found in the east and it is unclear whether these are variations of the local population or introgression through releases of captive-bred birds. Reintroduction efforts have clouded the natural patterns of variation, rendering the subspecies names less meaningful.

Wild Turkey (Eastern ) – Meleagris gallopavo silvestris

Wild Turkey (Merriam’s or Southwestern) – Meleagris gallopavo merriami

Family Gaviidae – Loons

Red-throated Loon – Gavia stellata

Arctic Loon – Gavia arctica

Pacific Loon – Gavia pacifica

Common Loon – Gavia immer

Yellow-billed Loon – Gavia adamsii

Family Podicipedidae – Grebes

Least Grebe – Tachybaptus dominicus

Pied-billed Grebe – Podilymbus podiceps

Horned Grebe – Podiceps auritus

Red-necked Grebe – Podiceps grisegena

Eared Grebe – Podiceps nigricollis

Western Grebe – Aechmophorus occidentalis

Clark’s Grebe – Aechmophorus clarkii

Family Phoenicopteridae – Flamingos

American Flamingo – Phoenicopterus ruber

Family Diomedeidae – Albatrosses

Yellow-nosed Albatross – Thalassarche chlororhynchos

All identifiable North American records are of the expected Atlantic subspecies T. c. chlororhynchos. The Indian Ocean form T. c. carteri is split by many authorities.

Shy Albatross – Thalassarche cauta

The few North American occurrences include confirmed records of cauta and well-documented records of birds showing the features of salvini. These are considered separate species by most authorities.

Shy Albatross (White-capped) – Thalassarche cauta cauta *

Shy Albatross (Salvin’s) – Thalassarche cauta salvini *

Black-browed Albatross – Thalassarche melanophris

North American records to date involve the expected T. m. melanophris. The New Zealand breeding subspecies T. m. impavida is split by some authorities.

Light-mantled Albatross – Phoebetria palpebrata

Wandering Albatross – Diomedea exulans

This species is now split by many authorities into four separate species. Of two North American records, one in Oregon was identified as the New Zealand breeding D. e. antipodensis and one from California could have been that subspecies or the nominate. Any future record will have to be carefully studied to determine its subspecies/species.

Laysan Albatross – Phoebastria immutabilis

Black-footed Albatross – Phoebastria nigripes

Short-tailed Albatross – Phoebastria albatrus

Family Procellariidae – Shearwaters and Petrels

Northern Fulmar – Fulmarus glacialis

Two subspecies groups are reliably distinguished by plumage and also differ in DNA and slightly in bill size and proportions.

Northern Fulmar (Atlantic) – Fulmarus glacialis glacialis group *

Northern Fulmar (Pacific) – Fulmarus glacialis rodgersii *

Great-winged Petrel – Pterodroma macroptera

North American records refer to P. m. gouldi

Herald Petrel – Pterodroma arminjoniana

Many authorities split the Atlantic form, which accounts for all North American records, as Trindade Petrel P. arminjoniana.

Murphy’s Petrel – Pterodroma ultima

Fea’s Petrel – Pterodroma feae

Now split from Zino’s Petrel (P. madeira), and some authorities further split Desertas Petrel (P. deserta), both of which are potential visitors to North America.

Mottled Petrel – Pterodroma inexpectata

Bermuda Petrel – Pterodroma cahow

Black-capped Petrel – Pterodroma hasitata

Observers off North Carolina have identified two or three distinct types there based on plumage and bill size, which might represent separate populations, but further study is needed to clarify the situation.

Hawaiian or Galapagos Petrel – Pterodroma sandwichensis or phaeopygia

Formerly Dark-rumped Petrel but now split into two species. It has been argued that records to date in North America involve Hawaiian Petrel, but this is not confirmed and both could occur.

Cook’s Petrel – Pterodroma cookii

Stejneger’s Petrel – Pterodroma longirostris

Bulwer’s Petrel – Bulweria bulwerii

White-chinned Petrel – Procellaria aequinoctialis

Parkinson’s Petrel – Procellaria parkinsoni

Streaked Shearwater – Calonectris leucomelas

Cory’s Shearwater – Calonectris diomedea

Two subspecies groups differ on average in size, plumage, and voice, but there is some overlap and the possibility of distinguishing them reliably in the field remains to be confirmed.

Cory’s Shearwater (Mediterranean or Scopoli’s) – Calonectris diomedea diomedea

Cory’s Shearwater (Atlantic) – Calonectris diomedea borealis

Cape Verde Shearwater – Calonectris edwardsii

Pink-footed Shearwater – Puffinus creatopus

Flesh-footed Shearwater – Puffinus carneipes

Great Shearwater – Puffinus gravis

Wedge-tailed Shearwater – Puffinus pacificus

Buller’s Shearwater – Puffinus bulleri

Sooty Shearwater – Puffinus griseus

Short-tailed Shearwater – Puffinus tenuirostris

Manx Shearwater – Puffinus puffinus

Townsend’s Shearwater – Puffinus auricularis

Black-vented Shearwater – Puffinus opisthomelas

Little Shearwater – Puffinus assimilis

Confirmed North American records in MA and NS refer to the Azores breeding form Barolo Shearwater P. a baroli which most authorities split from Little Shearwater. One report off California, if accepted, almost certainly refers to a different subspecies (species) and other forms could occur.

Audubon’s Shearwater – Puffinus lherminieri

Family Hydrobatidae – Storm-Petrels

Wilson’s Storm-Petrel – Oceanites oceanicus

White-faced Storm-Petrel – Pelagodroma marina

European Storm-Petrel – Hydrobates pelagicus

Two separate breeding populations (Atlantic and Mediterranean) differ in size and voice and have been split by some authorities, but they may not be distinguishable in the field. The few North American records presumably represent the Atlantic-breeding population, but confirmation is needed.

Black-bellied Storm-Petrel – Fregetta tropica

Fork-tailed Storm-Petrel – Oceanodroma furcata

Northern and Southern breeding populations differ in overall plumage color and average size and might just be identifiable in the field.

Ringed Storm-Petrel – Oceanodroma hornbyi

Leach’s Storm-Petrel – Oceanodroma leucorhoa

Four subspecies present a confusing mosaic of variation, with differences in size, structure, plumage color, habits, voice, and time of breeding. Relatively large and white-rumped birds are widespread in the Atlantic and North Pacific, while smaller white- and dark-rumped populations occur off Southern California. Probably best considered three populations, but how best to divide this variation into identifiable forms, and how reliably they can be identified in the field, remains to be determined. ––Read more…

Swinhoe’s Storm-Petrel – Oceanodroma monorhis

Ashy Storm-Petrel – Oceanodroma homochroa

Band-rumped Storm-Petrel – Oceanodroma castro

North Atlantic populations of this species may be split into three or four species, which will be extremely difficult to distinguish at sea. More study is needed.

Wedge-rumped Storm-Petrel – Oceanodroma tethys

Black Storm-Petrel – Oceanodroma melania

Tristram’s Storm-Petrel – Oceanodroma tristrami

Least Storm-Petrel – Oceanodroma microsoma

Family Phaethontidae – Tropicbirds

White-tailed Tropicbird – Phaethon lepturus

Red-billed Tropicbird – Phaethon aethereus

Red-tailed Tropicbird – Phaethon rubricauda

Family Ciconiidae – Storks

Jabiru – Jabiru mycteria

Wood Stork – Mycteria americana

Family Fregatidae – Frigatebirds

Magnificent Frigatebird – Fregata magnificens

Great Frigatebird – Fregata minor

Lesser Frigatebird – Fregata ariel

Family Sulidae – Boobies

Masked Booby – Sula dactylatra

Blue-footed Booby – Sula nebouxii

Brown Booby – Sula leucogaster

Adult males are reliably distinguished by head color. No other differences are known, so while a pale-headed bird in the Atlantic could probably be reliably identified as a vagrant from the Pacific, no other age/sex class can be identified.

Brown Booby (Eastern Pacific or Brewster’s) – Sula leucogaster brewsteri

Brown Booby (Atlantic) – Sula leucogaster leucogaster

Red-footed Booby – Sula sula

Some differences between Atlantic and Pacific forms may allow identification, but more study is needed.

Northern Gannet – Morus bassanus

Family Phalacrocoracidae – Cormorants

Brandt’s Cormorant – Phalacrocorax penicillatus

Neotropic Cormorant – Phalacrocorax brasilianus

Double-crested Cormorant – Phalacrocorax auritus

Some western birds have obvious white crests in breeding plumage and may be identifiable, but many have black crests like eastern birds.

Great Cormorant – Phalacrocorax carbo

Red-faced Cormorant – Phalacrocorax urile

Pelagic Cormorant – Phalacrocorax pelagicus

Family Anhingidae – Anhingas

Anhinga – Anhinga anhinga

Family Pelecanidae – Pelicans

American White Pelican – Pelecanus erythrorhynchos

Brown Pelican – Pelecanus occidentalis

Two populations usually differ in pouch color, but both colors are found in both populations, just in different frequencies. In practical terms this means that a vagrant cannot be identified. ––Read more…

Family Ardeidae – Herons and Egrets

American Bittern – Botaurus lentiginosus

Yellow Bittern – Ixobrychus sinensis

Least Bittern – Ixobrychus exilis

Bare-throated Tiger-Heron – Tigrisoma mexicanum

Great Blue Heron – Ardea herodias

The restricted population in the Florida Keys differs from the widespread birds in average size, average plume length, and color (all-white). These have been split as Great White Heron in the past, but whether this population is best considered a species, subspecies, or merely a morph is still a subject of debate. ––Read more…

Great Blue Heron (Typical) – Ardea herodias herodias group

Great Blue Heron (Great White) – Ardea herodias occidentalis

Grey Heron – Ardea cinerea

Great Egret – Ardea alba

Records in Virginia and western Alaska have been suspected of being the African and Asian subspecies, respectively, which may be elevated to species status, but identification has not been confirmed and ID criteria need to be worked out.

Intermediate Egret – Mesophoyx intermedia

Chinese Egret – Egretta eulophotes

Little Egret – Egretta garzetta

Western Reef-Heron – Egretta gularis

Snowy Egret – Egretta thula

Little Blue Heron – Egretta caerulea

Tricolored Heron – Egretta tricolor

Reddish Egret – Egretta rufescens

Cattle Egret – Bubulcus ibis

The Western subspecies is widespread in North America; Eastern (Asian) has been recorded at least once in western Alaska. It differs in size and breeding plumage, and is split by several authorities.

Cattle Egret (Western or African) – Bubulcus ibis ibis group

Cattle Egret (Eastern or Asian) – Bubulcus ibis coromandus

Chinese Pond-Heron – Ardeola bacchus

Green Heron – Butorides virescens

Black-crowned Night-Heron – Nycticorax nycticorax

Eurasian form presumably accounts for records in Aleutian Islands, but unconfirmed. Differences are slight.

Black-crowned Night-Heron (Eurasian) – Nycticorax nycticorax nycticorax

Black-crowned Night-Heron (American) – Nycticorax nycticorax hoactli

Yellow-crowned Night-Heron – Nyctanassa violacea

Family Threskiornithidae – Ibises and Spoonbills

White Ibis – Eudocimus albus

Scarlet Ibis – Eudocimus ruber

Glossy Ibis – Plegadis falcinellus

White-faced Ibis – Plegadis chihi

Roseate Spoonbill – Platalea ajaja

Family Cathartidae – New World Vultures

Black Vulture – Coragyps atratus

Turkey Vulture – Cathartes aura

California Condor – Gymnogyps californianus

Family Pandionidae – Osprey

Osprey – Pandion haliaetus

Breeders of Florida and the West Indies differ in head pattern, but probably not reliably identified out of range. Eurasian populations (unrecorded in North America) are split by many authorities.

Family Accipitridae – Hawks and Eagles

Hook-billed Kite – Chondrohierax uncinatus

Swallow-tailed Kite – Elanoides forficatus

White-tailed Kite – Elanus leucurus

Snail Kite – Rostrhamus sociabilis

Mississippi Kite – Ictinia mississippiensis

Bald Eagle – Haliaeetus leucocephalus

White-tailed Eagle – Haliaeetus albicilla

Steller’s Sea-Eagle – Haliaeetus pelagicus

Northern Harrier – Circus cyaneus

Most authorities split the Eurasian populations as Hen Harrier C. cyaneus (unrecorded in North America) from American C, hudsonius

Sharp-shinned Hawk – Accipiter striatus

Cooper’s Hawk – Accipiter cooperii

Northern Goshawk – Accipiter gentilis

Crane Hawk – Geranospiza caerulescens

Common Black-Hawk – Buteogallus anthracinus

Harris’s Hawk – Parabuteo unicinctus

Roadside Hawk – Buteo magnirostris

Red-shouldered Hawk – Buteo lineatus

Eastern and Florida populations differ from each other only in plumage color saturation. California birds are more distinctive (especially juvenile plumage) and should be identifiable in virtually all cases.

Red-shouldered Hawk (Eastern) – Buteo lineatus lineatus group

Red-shouldered Hawk (Florida) – Buteo lineatus extimus

Red-shouldered Hawk (California) – Buteo lineatus elegans

Broad-winged Hawk – Buteo platypterus

Gray Hawk – Buteo nitidus

Short-tailed Hawk – Buteo brachyurus

Swainson’s Hawk – Buteo swainsoni

White-tailed Hawk – Buteo albicaudatus

Zone-tailed Hawk – Buteo albonotatus

Red-tailed Hawk – Buteo jamaicensis

Most subspecies differ only slightly and on average in plumage, and are barely distinguishable except by subjective judgment and considering location. Krider’s may be only a morph. Harlan’s Hawk (B. j. harlani) is the exception, and is nearly 100% identifiable.

Red-tailed Hawk (Western) – Buteo jamaicensis calurus group

Red-tailed Hawk (Eastern) – Buteo jamaicensis borealis group

Red-tailed Hawk (Harlan’s) – Buteo jamaicensis harlani

Red-tailed Hawk (Krider’s) – Buteo jamaicensis kriderii

Red-tailed Hawk (Southwestern) – Buteo jamaicensis fuertesi

Ferruginous Hawk – Buteo regalis

Rough-legged Hawk – Buteo lagopus

Golden Eagle – Aquila chrysaetos

Family Falconidae – Falcons

Collared Forest-Falcon – Micrastur semitorquatus

Crested Caracara – Caracara cheriway

Eurasian Kestrel – Falco tinnunculus

American Kestrel – Falco sparverius

Red-footed Falcon – Falco vespertinus

Merlin – Falco columbarius

Three subspecies are usually identifiable by differences in overall color, although intergrades do occur and no differences in structure or voice are known. In addition, Siberian birds differ significantly in DNA, slightly in plumage. These have been reported in western Alaska but not confirmed.

Merlin (American Taiga) – Falco columbarius columbarius

Merlin (Prairie or Richardson’s) – Falco columbarius richardsonii

Merlin (Pacific or Black) – Falco columbarius suckleyi

Eurasian Hobby – Falco subbuteo

Aplomado Falcon – Falco femoralis

Gyrfalcon – Falco rusticolus

Peregrine Falcon – Falco peregrinus

Three subspecies differ slightly in details of plumage color and pattern. Most are probably identifiable with reasonable confidence, although the reintroduced populations in eastern US comprise a fourth group and can be confusingly similar to Continental and Peale’s.

Prairie Falcon – Falco mexicanus

Family Rallidae – Rails, Gallinules, and Coots

Yellow Rail – Coturnicops noveboracensis

Black Rail – Laterallus jamaicensis

Corn Crake – Crex crex

Clapper Rail – Rallus longirostris

Atlantic and Gulf Coast forms differ from each other only in overall plumage tones and average size, and are connected by intermediate populations. California population is separate and distinctive, differing in plumage, shape, and DNA.

Clapper Rail (Eastern) – Rallus longirostris crepitans group

Clapper Rail (California) – Rallus longirostris obsoletus group

King Rail – Rallus elegans

Virginia Rail – Rallus limicola

Sora – Porzana carolina

Paint-billed Crake – Neocrex erythrops

Spotted Rail – Pardirallus maculatus

Purple Swamphen – Porphyrio porphyrio

Purple Gallinule – Porphyrio martinica

Common Moorhen – Gallinula chloropus

Eurasian Coot – Fulica atra

American Coot – Fulica americana

White-shielded birds are merely a morph of American Coot and not Caribean Coot. ––Read more…

Family Heliornithidae – Sungrebes

Sungrebe – Heliornis fulica

Family Aramidae – Limpkin

Limpkin – Aramus guarauna

Family Gruidae – Cranes

Sandhill Crane – Grus canadensis

Extremes of size are distinctive and reliably identifiable, but G. c. rowani is intermediate in size. In California, for example, rowani does not occur so two distinct size classes are present. In most of North America rowani is common and a complete range of size is apparent.

Sandhill Crane (Lesser or Northern) – Grus canadensis canadensis

Sandhill Crane (Greater or Southern) – Grus canadensis pratensis group

Common Crane – Grus grus

Whooping Crane – Grus americana

Family Burhinidae – Thick-knees

Double-striped Thick-knee – Burhinus bistriatus

Family Charadriidae – Plovers and Lapwings

Northern Lapwing – Vanellus vanellus

Black-bellied Plover – Pluvialis squatarola

European Golden-Plover – Pluvialis apricaria

American Golden-Plover – Pluvialis dominica

Pacific Golden-Plover – Pluvialis fulva

Lesser Sand-Plover – Charadrius mongolus

Some authorities split the Northern mongolusatrifrons group. All North American records to date are the subspecies C. m. stegmanni of the mongolus group.

Greater Sand-Plover – Charadrius leschenaultii

Collared Plover – Charadrius collaris

Snowy Plover – Charadrius alexandrinus

Old World forms differ significantly in DNA and voice, slightly in plumage and are often split as Kentish Plover C. alexandrinus, but have not been recorded in North America. North American birds then become C. nivosus.

Wilson’s Plover – Charadrius wilsonia

Common Ringed Plover – Charadrius hiaticula

Semipalmated Plover – Charadrius semipalmatus

Piping Plover – Charadrius melodus

Little Ringed Plover – Charadrius dubius

Killdeer – Charadrius vociferus

Mountain Plover – Charadrius montanus

Eurasian Dotterel – Charadrius morinellus

Family Haematopodidae – Oystercatchers

Eurasian Oystercatcher – Haematopus ostralegus

American Oystercatcher – Haematopus palliatus

Two subspecies reliably distinguished by wing and tail pattern and completely separated by range.

American Oystercatcher (Atlantic) – Haematopus palliatus palliatus

American Oystercatcher (Pacific) – Haematopus palliatus frazari

Black Oystercatcher – Haematopus bachmani

Family Recurvirostridae – Avocets and Stilts

Black-winged Stilt – Himantopus himantopus

Black-necked Stilt – Himantopus mexicanus

One record (in Tennessee) of a bird showing characteristic of the South American subspecies H. m. melanurus but whether this was an actual vagrant from South America or a variant of the local population is unknown.

American Avocet – Recurvirostra americana

Family Jacanidae – Jacanas

Northern Jacana – Jacana spinosa

Family Scolopacidae – Sandpipers

Terek Sandpiper – Xenus cinereus

Common Sandpiper – Actitis hypoleucos

Spotted Sandpiper – Actitis macularius

Green Sandpiper – Tringa ochropus

Solitary Sandpiper – Tringa solitaria

Two subspecies (Eastern and Western) differ substantially in DNA, but apparently very little in plumage and no differences are known in voice or behavior. Criteria for identification in the field remain to be discovered.

Solitary Sandpiper (Eastern) – Tringa solitaria solitaria

Solitary Sandpiper (Western) – Tringa solitaria cinnamomea

Gray-tailed Tattler – Tringa brevipes

Wandering Tattler – Tringa incana

Spotted Redshank – Tringa erythropus

Greater Yellowlegs – Tringa melanoleuca

Common Greenshank – Tringa nebularia

Willet – Tringa semipalmata

Two subspecies differ fundamentally in appearance, voice, and migratory routes.

Willet (Eastern) – Tringa semipalmata semipalmata *

Willet (Western) – Tringa semipalmata inornata *

Lesser Yellowlegs – Tringa flavipes

Marsh Sandpiper – Tringa stagnatilis

Wood Sandpiper – Tringa glareola

Common Redshank – Tringa totanus

Upland Sandpiper – Bartramia longicauda

Little Curlew – Numenius minutus

Whimbrel – Numenius phaeopus

Three subspecies all readily identifiable by plumage, but no reliable differences known in structure or voice. European and Asian forms are rare visitors to North America, and DNA studies reveal a substantial difference between American and Asian subspecies.

Whimbrel (European) – Numenius phaeopus phaeopus *

Whimbrel (Asian) – Numenius phaeopus variegatus *

Whimbrel (American) – Numenius phaeopus hudsonicus *

Bristle-thighed Curlew – Numenius tahitiensis

Far Eastern Curlew – Numenius madagascariensis

Slender-billed Curlew – Numenius tenuirostris

Eurasian Curlew – Numenius arquata

Long-billed Curlew – Numenius americanus

Black-tailed Godwit – Limosa limosa

Three subspecies, all rare visitors to North America. Icelandic and European are barely distinguishable, but Asian differs in size and DNA and is split by some authorities, although field ID criteria still need to be worked out.

Black-tailed Godwit (European) – Limosa limosa limosa

Black-tailed Godwit (Icelandic) – Limosa limosa islandica

Black-tailed Godwit (Asian) – Limosa limosa melanuroides

Hudsonian Godwit – Limosa haemastica

Bar-tailed Godwit – Limosa lapponica

European and Asian forms are readily distinguished in the field by plumage.

Bar-tailed Godwit (European or Western) – Limosa lapponica lapponica

Bar-tailed Godwit (Asian or Eastern) – Limosa lapponica baueri

Marbled Godwit – Limosa fedoa

Ruddy Turnstone – Arenaria interpres

Black Turnstone – Arenaria melanocephala

Surfbird – Aphriza virgata

Great Knot – Calidris tenuirostris

Red Knot – Calidris canutus

Sanderling – Calidris alba

Semipalmated Sandpiper – Calidris pusilla

Western Sandpiper – Calidris mauri

Red-necked Stint – Calidris ruficollis

Little Stint – Calidris minuta

Temminck’s Stint – Calidris temminckii

Long-toed Stint – Calidris subminuta

Least Sandpiper – Calidris minutilla

White-rumped Sandpiper – Calidris fuscicollis

Baird’s Sandpiper – Calidris bairdii

Pectoral Sandpiper – Calidris melanotos

Sharp-tailed Sandpiper – Calidris acuminata

Purple Sandpiper – Calidris maritima

Rock Sandpiper – Calidris ptilocnemis

Pribilof population is distinctive in size and plumage. Aleutian and Mainland subspecies are similar to each other and are lumped here, but it may be possible to distinguish them as well.

Rock Sandpiper (Pribilof) – Calidris ptilocnemis ptilocnemis

Rock Sandpiper (Aleutian/Mainland) – Calidris ptilocnemis couesi group

Dunlin – Calidris alpina

Greenland Dunlin a very rare visitor to eastern North America and readily identifiable. Recent research shows that American Dunlin comprise more than one population – Dunlin in western North America are disjunct from eastern birds and distinct genetically, but field ID, if possible, still needs to be sorted out.

Dunlin (American) – Calidris alpina pacifica group *

Dunlin (Greenland) – Calidris alpina arctica group *

Curlew Sandpiper – Calidris ferruginea

Stilt Sandpiper – Calidris himantopus

Spoon-billed Sandpiper – Eurynorhynchus pygmeus

Broad-billed Sandpiper – Limicola falcinellus

Buff-breasted Sandpiper – Tryngites subruficollis

Ruff – Philomachus pugnax

Short-billed Dowitcher – Limnodromus griseus

Three subspecies more or less identifiable in breeding plumage, but not at other times. No differences in structure or voice.

Short-billed Dowitcher (Atlantic) – Limnodromus griseus griseus

Short-billed Dowitcher (Central or Henderson’s) – Limnodromus griseus hendersoni

Pacific Short-billed Dowitcher – Limnodromus griseus caurinus

Long-billed Dowitcher – Limnodromus scolopaceus

Jack Snipe – Lymnocryptes minimus

Solitary Snipe – Gallinago solitaria

Wilson’s Snipe – Gallinago delicata

Common Snipe – Gallinago gallinago

Pin-tailed Snipe – Gallinago stenura

Eurasian Woodcock – Scolopax rusticola

American Woodcock – Scolopax minor

Wilson’s Phalarope – Phalaropus tricolor

Red-necked Phalarope – Phalaropus lobatus

Red Phalarope – Phalaropus fulicarius

Family Glareolidae – Pratincoles

Oriental Pratincole – Glareola maldivarum

Family Laridae – Gulls and Terns

Swallow-tailed Gull – Creagrus furcatus

Black-legged Kittiwake – Rissa tridactyla

Two subspecies (Pacific and Atlantic) are distinguished by average differences in wingtip pattern and voice, but probably not identifiable in the field.

Red-legged Kittiwake – Rissa brevirostris

Ivory Gull – Pagophila eburnea

Sabine’s Gull – Xema sabini

Bonaparte’s Gull – Chroicocephalus philadelphia

Gray-hooded Gull – Chroicocephalus cirrocephalus

Black-headed Gull – Chroicocephalus ridibundus

Little Gull – Hydrocoloeus minutus

Ross’s Gull – Rhodostethia rosea

Laughing Gull – Leucophaeus atricilla

Franklin’s Gull – Leucophaeus pipixcan

Belcher’s Gull – Larus belcheri

Black-tailed Gull – Larus crassirostris

Heermann’s Gull – Larus heermanni

Mew Gull – Larus canus

Three subspecies. The American Mew Gull is distinctive, especially in immature plumage, and is often split from the others. Kamchatka and Common Gull are fairly distinct from each other and usually identifiable in the field.

Mew Gull (European or Common Gull) – Larus canus canus group *

Mew Gull (Kamchatka or Siberian) – Larus canus kamtschatschensis

Mew Gull (Short-billed or American) – Larus canus brachyrhynchus *

Ring-billed Gull – Larus delawarensis

Western Gull – Larus occidentalis

Two subspecies differ only in average shade of gray on the mantle and average size, and are not reliably identified in the field

Yellow-footed Gull – Larus livens

California Gull – Larus californicus

Two subspecies differ only in average size and shade of gray on the mantle and are not reliably identified in the field

Herring Gull – Larus argentatus

Three subspecies groups are all fairly distinctive and usually identifiable (with very careful study) in the field, but most distinctive in juvenal plumage. Many authorities now split them into three species.

Herring Gull (American or Smithsonian) – Larus argentatus smithsonianus

Herring Gull (Vega or Siberian) – Larus argentatus vegae

Herring Gull (European) – Larus argentatus argentatus group

Yellow-legged Gull – Larus michahellis

Thayer’s Gull – Larus thayeri

Iceland Gull – Larus glaucoides

Two subspecies differ in average wingtip pattern and average size, but overlap in all features makes field identification essentially impossible in North America, where the white-winged subspecies L. g. glaucoides is probably a rare visitor but is apparently matched by some pale L. g. kumlieni

Lesser Black-backed Gull – Larus fuscus

Two subspecies have occurred in North America, but differ only in average darkness of adult mantle color, with intermediates, so identification is somewhat tenuous.

Slaty-backed Gull – Larus schistisagus

Glaucous-winged Gull – Larus glaucescens

Siberian breeders differ at least from Washington breeders in long call, and possibly in average adult leg color and mantle color. More study is needed to determine the extent and geographic pattern of differences.

Glaucous Gull – Larus hyperboreus

Average regional differences in size and mantle color are not sufficient for reliable identificiton out of range.

Great Black-backed Gull – Larus marinus

Kelp Gull – Larus dominicanus

Brown Noddy – Anous stolidus

Black Noddy – Anous minutus

Sooty Tern – Onychoprion fuscatus

Bridled Tern – Onychoprion anaethetus

Aleutian Tern – Onychoprion aleuticus

Least Tern – Sternula antillarum

Large-billed Tern – Phaetusa simplex

Gull-billed Tern – Gelochelidon nilotica

Caspian Tern – Hydroprogne caspia

Black Tern – Chlidonias niger

White-winged Tern – Chlidonias leucopterus

Whiskered Tern – Chlidonias hybrida

Roseate Tern – Sterna dougallii

Common Tern – Sterna hirundo

Two subspecies are probably reliably identified by bill and leg color in breeding plumage but not at other times. Asian a rare visitor to western Alaska.

Common Tern (Western or American/European) – Sterna hirundo hirundo

Common Tern (Asian) – Sterna hirundo longipennis

Arctic Tern – Sterna paradisaea

Forster’s Tern – Sterna forsteri

Royal Tern – Thalasseus maximus

Sandwich Tern – Thalasseus sandvicensis

Two subspecies reliably identified by bill color, although mixed breeding colonies in the Caribbean suggest that these might be considered morphs. European populations recently split by some authorities as Sandwich Tern T. sandvicensis, and could occur in North America (one potential record from Illinois).

Sandwich Tern (American or Cabot’s) – Thalasseus sandvicensis acuflavidus

Sandwich Tern (Cayenne Tern) – Thalasseus sandvicensis eurygnathus

Elegant Tern – Thalasseus elegans

Black Skimmer – Rynchops niger

Family Stercorariidae – Skuas and Jaegers

Great Skua – Stercorarius skua

The AOU still lumps the Antarctic skuas in this species. Those are split by most authorities as Brown Skua C. antarcticus with confirmed records (by DNA) in Britain, and suspected records off eastern US.

South Polar Skua – Stercorarius maccormicki

Pomarine Jaeger – Stercorarius pomarinus

Parasitic Jaeger – Stercorarius parasiticus

Long-tailed Jaeger – Stercorarius longicaudus

Family Alcidae – Alcids

Dovekie – Alle alle

Common Murre – Uria aalge

Pacific and Atlantic populations differ in bill shape, but whether this would be sufficient to identify a bird out-of-range is unknown.

Thick-billed Murre – Uria lomvia

Pacific and Atlantic populations differ in bill shape, but whether this would be sufficient to identify a bird out-of-range is unknown.

Razorbill – Alca torda

Black Guillemot – Cepphus grylle

Two subspecies differ in overall color in non-breeding plumages, but how reliably these can be distinguished is unknown.

Black Guillemot (Arctic) – Cepphus grylle mandtii

Black Guillemot (Atlantic) – Cepphus grylle arcticus group

Pigeon Guillemot – Cepphus columba

Long-billed Murrelet – Brachyramphus perdix

Marbled Murrelet – Brachyramphus marmoratus

Kittlitz’s Murrelet – Brachyramphus brevirostris

Xantus’s Murrelet – Synthliboramphus hypoleucus

Two subspecies differ in plumage and voice and are always readily identified.

Xantus’ Murrelet (Northern or Scripps’s) – Synthliboramphus hypoleucus scrippsi *

Xantus’ Murrelet (Southern) – Synthliboramphus hypoleucus hypoleucus *

Craveri’s Murrelet – Synthliboramphus craveri

Ancient Murrelet – Synthliboramphus antiquus

Cassin’s Auklet – Ptychoramphus aleuticus

Parakeet Auklet – Aethia psittacula

Least Auklet – Aethia pusilla

Whiskered Auklet – Aethia pygmaea

Crested Auklet – Aethia cristatella

Rhinoceros Auklet – Cerorhinca monocerata

Atlantic Puffin – Fratercula arctica

Horned Puffin – Fratercula corniculata

Tufted Puffin – Fratercula cirrhata

Family Columbidae – Pigeons and Doves

Rock Pigeon – Columba livia

Scaly-naped Pigeon – Patagioenas squamosa

White-crowned Pigeon – Patagioenas leucocephala

Red-billed Pigeon – Patagioenas flavirostris

Band-tailed Pigeon – Patagioenas fasciata

European Turtle-Dove – Streptopelia turtur

Oriental Turtle-Dove – Streptopelia orientalis

Eurasian Collared-Dove – Streptopelia decaocto

Spotted Dove – Streptopelia chinensis

White-winged Dove – Zenaida asiatica

Zenaida Dove – Zenaida aurita

Mourning Dove – Zenaida macroura

Inca Dove – Columbina inca

Common Ground-Dove – Columbina passerina

Eastern and Western subspecies differ only on average in overall plumage color, and are too variable to allow identification outside their normal range.

Ruddy Ground-Dove – Columbina talpacoti

Eastern and Western subspecies differ only on average in overall plumage color. Some extremes might be identifiable but color is so variable with age and sex that most probably cannot be identified to subspecies outside their normal range.

White-tipped Dove – Leptotila verreauxi

Key West Quail-Dove – Geotrygon chrysia

Ruddy Quail-Dove – Geotrygon montana

Family Psittacidae – Parrots

Budgerigar – Melopsittacus undulatus

Monk Parakeet – Myiopsitta monachus

Green Parakeet – Aratinga holochlora

Thick-billed Parrot – Rhynchopsitta pachyrhyncha

White-winged Parakeet – Brotogeris versicolurus

Red-crowned Parrot – Amazona viridigenalis

Family Cuculidae – Cuckoos

Common Cuckoo – Cuculus canorus

Oriental Cuckoo – Cuculus optatus

Yellow-billed Cuckoo – Coccyzus americanus

Mangrove Cuckoo – Coccyzus minor

Black-billed Cuckoo – Coccyzus erythropthalmus

Greater Roadrunner – Geococcyx californianus

Smooth-billed Ani – Crotophaga ani

Groove-billed Ani – Crotophaga sulcirostris

Family Tytonidae – Barn Owls

Barn Owl – Tyto alba

Family Strigidae – Typical Owls

Flammulated Owl – Otus flammeolus

Oriental Scops-Owl – Otus sunia

Western Screech-Owl – Megascops kennicottii

Subspecies variation appears to be clinal, involving size and average color, but a recent DNA barcode study revealed substantial differences between some populations. More study is needed.

Eastern Screech-Owl – Megascops asio

Subspecies variation is clinal, involving size and average color, although it has been suggested that the South Texas population might be more distinctive, with slightly different vocalizations.

Whiskered Screech-Owl – Megascops trichopsis

Great Horned Owl – Bubo virginianus

Subspecies variation is clinal, mostly involving average color. In any specific location it should be possible to identify a visitor from a nearby region, and some subspecies are fairly distinctive, but more study is needed to define any regional groups.

Snowy Owl – Bubo scandiacus

Northern Hawk Owl – Surnia ulula

Northern Pygmy-Owl – Glaucidium gnoma

Three subspecies groups differ in voice and only very slightly in plumage and size. These have been proposed for splitting but more info is needed on the extent and reliability of differences.

Northern Pygmy-Owl (Mexican or Mountain) – Glaucidium gnoma gnoma

Northern Pygmy-Owl (Pacific) – Glaucidium gnoma californicum group

Northern Pygmy-Owl (Interior West or Mountain) – Glaucidium gnoma pinicola group

Ferruginous Pygmy-Owl – Glaucidium brasilianum

Elf Owl – Micrathene whitneyi

Burrowing Owl – Athene cunicularia

Two subspecies are readily identified by plumage.

Burrowing Owl (Western) – Athene cunicularia hypugaea

Burrowing Owl (Florida) – Athene cunicularia floridana

Mottled Owl – Ciccaba virgata

Spotted Owl – Strix occidentalis

Two subspecies groups differ in overall plumage color and DNA, probably barely identifiable.

Spotted Owl (Northern) – Strix occidentalis occidentalis group

Spotted Owl (Mexican) – Strix occidentalis lucida

Barred Owl – Strix varia

Great Gray Owl – Strix nebulosa

Long-eared Owl – Asio otus

Stygian Owl – Asio stygius

Short-eared Owl – Asio flammeus

Two subspecies readily identified by plumage. Other subspecies occur outside North America.

Short-eared Owl (Northern) – Asio flammeus flammeus *

Short-eared Owl (Antillean) – Asio flammeus domingensis group *

Boreal Owl – Aegolius funereus

Siberian form recorded once in Alaska (Pribilof Islands, Jan 1911) much paler than American and probably readily distinguished in the field, and DNA barcode study shows substantial difference from North American.

Boreal Owl (Tengmalm’s or Siberian) – Aegolius funereus magnus

Boreal Owl (American) – Aegolius funereus richardsoni

Northern Saw-whet Owl – Aegolius acadicus

No known variation in most of North America but the Queen Charlotte Islands, BC, population is distinctly darker and might be recognizable in the field.

Brown Hawk-Owl – Ninox scutulata

Family Caprimulgidae – Nightjars

Lesser Nighthawk – Chordeiles acutipennis

Common Nighthawk – Chordeiles minor

Subspecies differ in size and average color, but only the juvenal plumage of Great Plains birds is distinctive enough to be identifiable.

Common Nighthawk (Typical) – Chordeiles minor minor group

Common Nighthawk (Plains) – Chordeiles minor sennetti group

Antillean Nighthawk – Chordeiles gundlachii

Common Pauraque – Nyctidromus albicollis

Common Poorwill – Phalaenoptilus nuttallii

Chuck-will’s-widow – Caprimulgus carolinensis

Buff-collared Nightjar – Caprimulgus ridgwayi

Eastern Whip-poor-will – Caprimulgus vociferus

Mexican Whip-poor-will – Caprimulgus arizonae

Gray Nightjar – Caprimulgus indicus

Family Apodidae – Swifts

Black Swift – Cypseloides niger

White-collared Swift – Streptoprocne zonaris

Chimney Swift – Chaetura pelagica

Vaux’s Swift – Chaetura vauxi

Two subspecies (Mexican subspecies C. v. tamaulipensis a very rare visitor to the US) are readily distinguished in the hand. Identifying them in the field will be more difficult, but should be possible. ––Read more…

Vaux’s Swift (Northern) – Chaetura vauxi vauxi

Vaux’s Swift (Mexican) – Chaetura vauxi tamaulipensis [richmondi group]

White-throated Needletail – Hirundapus caudacutus

Common Swift – Apus apus

Fork-tailed Swift – Apus pacificus

White-throated Swift – Aeronautes saxatalis

Antillean Palm-Swift – Tachornis phoenicobia

Family Trochilidae – Hummingbirds

Green Violetear – Colibri thalassinus

Green-breasted Mango – Anthracothorax prevostii

Broad-billed Hummingbird – Cynanthus latirostris

White-eared Hummingbird – Hylocharis leucotis

Xantus’s Hummingbird – Hylocharis xantusii

Berylline Hummingbird – Amazilia beryllina

Buff-bellied Hummingbird – Amazilia yucatanensis

Cinnamon Hummingbird – Amazilia rutila

Violet-crowned Hummingbird – Amazilia violiceps

Blue-throated Hummingbird – Lampornis clemenciae

Magnificent Hummingbird – Eugenes fulgens

Plain-capped Starthroat – Heliomaster constantii

Bahama Woodstar – Calliphlox evelynae

Lucifer Hummingbird – Calothorax lucifer

Ruby-throated Hummingbird – Archilochus colubris

Black-chinned Hummingbird – Archilochus alexandri

Anna’s Hummingbird – Calypte anna

Costa’s Hummingbird – Calypte costae

Calliope Hummingbird – Stellula calliope

Bumblebee Hummingbird – Atthis heloisa

Broad-tailed Hummingbird – Selasphorus platycercus

Rufous Hummingbird – Selasphorus rufus

Allen’s Hummingbird – Selasphorus sasin

Birds of the Channel Islands and adjacent mainland average longer-billed with little overlap (sex for sex) but no other differences are known, intergradation probably occurs northwards, and it is generally not possible to identify this subspecies in the field.

Family Trogonidae – Trogons

Eared Quetzal – Euptilotis neoxenus

Elegant Trogon – Trogon elegans

Family Upupidae – Hoopoes

Eurasian Hoopoe – Upupa epops

Family Alcedinidae – Kingfishers

Ringed Kingfisher – Megaceryle torquata

Belted Kingfisher – Megaceryle alcyon

Amazon Kingfisher – Chloroceryle amazona

Green Kingfisher – Chloroceryle americana

Family Picidae – Woodpeckers

Eurasian Wryneck – Jynx torquilla

Lewis’s Woodpecker – Melanerpes lewis

Red-headed Woodpecker – Melanerpes erythrocephalus

Acorn Woodpecker – Melanerpes formicivorus

Subtle differences in average size and plumage might be sufficient to allow identification of subspecies in the field, but more study is needed to assess variation. No differences in voice are known.

Acorn Woodpecker (Pacific) – Melanerpes formicivorus bairdi

Acorn Woodpecker (Southwestern) – Melanerpes formicivorus formicivorus group

Gila Woodpecker – Melanerpes uropygialis

Golden-fronted Woodpecker – Melanerpes aurifrons

Red-bellied Woodpecker – Melanerpes carolinus

Birds of southern Florida differ on average in size and plumage, and may appear quite different from far northern birds, but variation is reportedly extensive and clinal, and some authorities do not even recognize a separate subspecies there. More study is needed to clarify the situation.

Williamson’s Sapsucker – Sphyrapicus thyroideus

Yellow-bellied Sapsucker – Sphyrapicus varius

Red-naped Sapsucker – Sphyrapicus nuchalis

Red-breasted Sapsucker – Sphyrapicus ruber

Two subspecies usually identifiable by plumage color.

Red-breasted Sapsucker (Northern) – Sphyrapicus ruber ruber

Red-breasted Sapsucker (Southern) – Sphyrapicus ruber daggetti

Great Spotted Woodpecker – Dendrocopos major

Ladder-backed Woodpecker – Picoides scalaris

Nuttall’s Woodpecker – Picoides nuttallii

Downy Woodpecker – Picoides pubescens

Three subspecies groups differ in plumage, but not voice or structure; many are probably identifiable but reliability of differences needs to be worked out.

Downy Woodpecker (Eastern) – Picoides pubescens pubescens group

Downy Woodpecker (Interior West) – Picoides pubescens leucurus group

Downy Woodpecker (Pacific) – Picoides pubescens gairdnerii group

Hairy Woodpecker – Picoides villosus

Four subspecies groups differ in plumage, and slightly in size, but not voice or structure; many are probably safely identifiable but reliability of differences needs to be worked out.

Hairy Woodpecker (Interior West) – Picoides villosus septentrionalis group

Hairy Woodpecker (Eastern) – Picoides villosus villosus group

Hairy Woodpecker (Pacific) – Picoides villosus harrisi group

Hairy Woodpecker (Mexican) – Picoides villosus icastus

Arizona Woodpecker – Picoides arizonae

Red-cockaded Woodpecker – Picoides borealis

White-headed Woodpecker – Picoides albolarvatus

American Three-toed Woodpecker – Picoides dorsalis

Three subspecies differ in overall darkness of plumage on average, but variation probably renders them unidentifiable in most cases.

Black-backed Woodpecker – Picoides arcticus

Northern Flicker – Colaptes auratus

Two populations reliably distinguished by multiple plumage differences, but intergrades are common across a very wide area.

Northern Flicker (Yellow-shafted) – Colaptes auratus auratus group

Northern Flicker (Red-shafted) – Colaptes auratus cafer group

Gilded Flicker – Colaptes chrysoides

Pileated Woodpecker – Dryocopus pileatus

Family Tyrannidae – Tyrant Flycatchers

Northern Beardless-Tyrannulet – Camptostoma imberbe

Greenish Elaenia – Myiopagis viridicata

White-crested Elaenia – Elaenia albiceps

Tufted Flycatcher – Mitrephanes phaeocercus

Olive-sided Flycatcher – Contopus cooperi

Breeders in southern California show slight average differences in size and plumage, but probably not sufficient for identification in the field. Birds of entire Pacific region (currently not distinguished as a subspecies) migrate much earlier in spring and seem to differ slightly in song from Taiga birds. More study is needed.

Greater Pewee – Contopus pertinax

Western Wood-Pewee – Contopus sordidulus

Eastern Wood-Pewee – Contopus virens

Cuban Pewee – Contopus caribaeus

Yellow-bellied Flycatcher – Empidonax flaviventris

Acadian Flycatcher – Empidonax virescens

Alder Flycatcher – Empidonax alnorum

Willow Flycatcher – Empidonax traillii

Two groups may be distinguishable in the field, with subtle differences in plumage and possibly in voice. More study is needed to determine the reliability of ID features.

Willow Flycatcher (Eastern) – Empidonax traillii traillii group

Willow Flycatcher (Western) – Empidonax traillii brewsteri group

Least Flycatcher – Empidonax minimus

Hammond’s Flycatcher – Empidonax hammondii

Gray Flycatcher – Empidonax wrightii

Dusky Flycatcher – Empidonax oberholseri

Pacific-slope Flycatcher – Empidonax difficilis

Channel Islands population differs very slightly in average color and song, but probably not safely identifiable in the field. In fact, recent evidence suggests that this species and Cordilleran Flycatcher – while distinctive in the southern (allopatric) parts of their ranges – intermix broadly in the north and might be better lumped as one species – Western Flycatcher.

Cordilleran Flycatcher – Empidonax occidentalis

Buff-breasted Flycatcher – Empidonax fulvifrons

Black Phoebe – Sayornis nigricans

Eastern Phoebe – Sayornis phoebe

Say’s Phoebe – Sayornis saya

Vermilion Flycatcher – Pyrocephalus rubinus

Dusky-capped Flycatcher – Myiarchus tuberculifer

Two subspecies (Eastern a rare visitor to Texas) are reliably distinguished by plumage.

Dusky-capped Flycatcher (West Mexican) – Myiarchus tuberculifer olivascens

Dusky-capped Flycatcher (East Mexican) – Myiarchus tuberculifer lawrenceii

Ash-throated Flycatcher – Myiarchus cinerascens

Nutting’s Flycatcher – Myiarchus nuttingi

Great Crested Flycatcher – Myiarchus crinitus

Brown-crested Flycatcher – Myiarchus tyrannulus

Western Mexican and Eastern Mexican populations differ only in average size (especially bill size) and are not safely identified in the field.

La Sagra’s Flycatcher – Myiarchus sagrae

Great Kiskadee – Pitangus sulphuratus

Social Flycatcher – Myiozetetes similis

Sulphur-bellied Flycatcher – Myiodynastes luteiventris

Piratic Flycatcher – Legatus leucophaius

Variegated Flycatcher – Empidonomus varius

Crowned Slaty Flycatcher – Empidonomus aurantioatrocristatus

Tropical Kingbird – Tyrannus melancholicus

Nominate subspecies of South America (recorded once in California and should be watched for elsewhere) differs in plumage color and might just be distinguishable in the field.

Couch’s Kingbird – Tyrannus couchii

Cassin’s Kingbird – Tyrannus vociferans

Thick-billed Kingbird – Tyrannus crassirostris

Western Kingbird – Tyrannus verticalis

Eastern Kingbird – Tyrannus tyrannus

Gray Kingbird – Tyrannus dominicensis

Loggerhead Kingbird – Tyrannus caudifasciatus

Scissor-tailed Flycatcher – Tyrannus forficatus

Fork-tailed Flycatcher – Tyrannus savana

Most North American records involve the South American subspecies, but a few have been identified as Mexican. Differences involve plumage, primary tip shape of male, and presumably molt timing, but reliability of these differences needs to be established.

Fork-tailed Flycatcher (South American) – Tyrannus savana savana group

Fork-tailed Flycatcher (Mexican) – Tyrannus savana monachus

Masked Tityra – Tityra semifasciata

Gray-collared Becard – Pachyramphus major

Rose-throated Becard – Pachyramphus aglaiae

Two subspecies are probably reliably separated by plumage, but this needs confirmation. Other subspecies farther south in Mexico intergrade.

Rose-throated Becard (West Mexican) – Pachyramphus aglaiae albiventris

Rose-throated Becard (East Mexican) – Pachyramphus aglaiae gravis

Family Laniidae – Shrikes

Brown Shrike – Lanius cristatus

Loggerhead Shrike – Lanius ludovicianus

Subspecies show slight and average differences in plumage, probably not reliably identifiable in the field.

Northern Shrike – Lanius excubitor

Siberian form recorded once in western Aleutians. More study is needed on visual ID criteria, but DNA barcode study shows substantial difference from North American.

Northern Shrike (American) – Lanius excubitor borealis group

Northern Shrike (Siberian or Great Grey) – Lanius excubitor sibiricus

Family Vireonidae – Vireos

White-eyed Vireo – Vireo griseus

Three subspecies in US differ in average size and plumage brightness. It is possible that some might be identifiable, but more study is needed.

Thick-billed Vireo – Vireo crassirostris

Bell’s Vireo – Vireo bellii

Two subspecies groups appear to be reliably distinguished by plumage, shape, and behavior.

Bell’s Vireo (Eastern) – Vireo bellii bellii

Bell’s Vireo (Southwestern) – Vireo bellii pusillus group

Black-capped Vireo – Vireo atricapilla

Gray Vireo – Vireo vicinior

Yellow-throated Vireo – Vireo flavifrons

Plumbeous Vireo – Vireo plumbeus

Cassin’s Vireo – Vireo cassinii

Blue-headed Vireo – Vireo solitarius

Hutton’s Vireo – Vireo huttoni

Two subspecies groups differ in overall plumage color and differ slightly in voice, but identification in the field would be a challenge.

Hutton’s Vireo (Pacific) – Vireo huttoni huttoni group

Hutton’s Vireo (Mexican) – Vireo huttoni stephensi group

Warbling Vireo – Vireo gilvus

Two subspecies groups differ on average in plumage, size, song, and DNA, and have often been discussed as potential species; but reliability of differences still has not been established and the possibility of identification in the field needs more study.

Warbling Vireo (Eastern) – Vireo gilvus gilvus

Warbling Vireo (Western) – Vireo gilvus swainsoni group

Philadelphia Vireo – Vireo philadelphicus

Red-eyed Vireo – Vireo olivaceus

Yellow-green Vireo – Vireo flavoviridis

Black-whiskered Vireo – Vireo altiloquus

Yucatan Vireo – Vireo magister

Family Corvidae – Crows and Jays

Gray Jay – Perisoreus canadensis

Three subspecies groups differ in plumage, and are identifiable in most cases, but intergrade where ranges meet. More study might reveal additional and more reliable differences.

Gray Jay (Taiga) – Perisoreus canadensis canadensis group

Gray Jay (Mountain) – Perisoreus canadensis capitalis group

Gray Jay (Pacific) – Perisoreus canadensis obscurus group

Steller’s Jay – Cyanocitta stelleri

Many named subspecies can be grouped in several different ways but variation is mostly clinal with many intergrades and no groups are very well-defined. Two subspecies groups listed here differ in plumage, and are identifiable in most cases. When study is limited to a single region it is often possible to identify a resident population and several different visiting forms. More study might reveal additional and more reliable differences.

Steller’s Jay (Pacific) – Cyanocitta stelleri stelleri group

Steller’s Jay (Mountain) – Cyanocitta stelleri diademata group

Blue Jay – Cyanocitta cristata

Green Jay – Cyanocorax yncas

Brown Jay – Psilorhinus morio

Florida Scrub-Jay – Aphelocoma coerulescens

Island Scrub-Jay – Aphelocoma insularis

Western Scrub-Jay – Aphelocoma californica

Two subspecies groups differ consistently in plumage and slightly in voice and behavior. Proposed as full species.

Western Scrub-Jay (Pacific) – Aphelocoma californica californica group *

Western Scrub-Jay (Interior West or Woodhouse’s) – Aphelocoma californica woodhouseii group *

Mexican Jay – Aphelocoma ultramarina

Two subspecies groups differ consistently in plumage and juvenile bill color, and slightly in voice and behavior. Could be considered for species status but connected by intermediate populations through Mexico.

Mexican Jay (Arizona) – Aphelocoma ultramarina arizonae [wollweberi group] *

Mexican Jay (Texas or Couch’s) – Aphelocoma ultramarina couchii group *

Pinyon Jay – Gymnorhinus cyanocephalus

Black-billed Magpie – Pica hudsonia

Yellow-billed Magpie – Pica nuttalli

Clark’s Nutcracker – Nucifraga columbiana

Eurasian Jackdaw – Corvus monedula

American Crow – Corvus brachyrhynchos

Northwestern Crow – Corvus caurinus

Tamaulipas Crow – Corvus imparatus

Fish Crow – Corvus ossifragus

Chihuahuan Raven – Corvus cryptoleucus

Common Raven – Corvus corax

Recent DNA studies reveal a significantly different population in California, which may also differ in size and proportions, but whether or not that form is identifiable in the field remains to be worked out.

Family Alaudidae – Larks

Sky Lark – Alauda arvensis

Introduced populations in British Columbia originated in England, while vagrants from Siberia have occurred in Alaska and very rarely farther south on the Pacific coast. The two might be reliably distinguishable by plumage.

Horned Lark – Eremophila alpestris

There are certainly several identifiable forms within this species. Similar to, for example, Great Horned Owl, variation is clinal and involves plumage color. A cursory grouping is offered here based on the Sibley Guide but a full and detailed review is needed.

Horned Lark (Asian) – Eremophila alpestris flava

Horned Lark (Western Arctic) – Eremophila alpestris alpestris group

Horned Lark (Northeastern) – Eremophila alpestris praticola

Horned Lark (East Mexican) – Eremophila alpestris giraudi

Horned Lark (Interior West) – Eremophila alpestris leucolaema

Horned Lark (West Mexican) – Eremophila alpestris occidentalis

Horned Lark (Pacific Northwest) – Eremophila alpestris strigata group

Horned Lark (California) – Eremophila alpestris rubea

Family Hirundinidae – Swallows and Martins

Northern Rough-winged Swallow – Stelgidopteryx serripennis

Purple Martin – Progne subis

Two subspecies groups differ in non-adult-male plumages, and may differ in voice. More study is needed to determine how reliably these can be distinguished in the field, and whether Southwestern desert birds belong with other western populations or as a separate group.

Purple Martin (Eastern) – Progne subis subis

Purple Martin (Western) – Progne subis hesperia group

Cuban Martin – Progne cryptoleuca

Gray-breasted Martin – Progne chalybea

Southern Martin – Progne elegans

Brown-chested Martin – Progne tapera

Tree Swallow – Tachycineta bicolor

Mangrove Swallow – Tachycineta albilinea

Violet-green Swallow – Tachycineta thalassina

Bahama Swallow – Tachycineta cyaneoviridis

Bank Swallow – Riparia riparia

Barn Swallow – Hirundo rustica

Two subspecies groups differ in plumage and DNA. All or nearly all are readily identifiable. Eurasian group a rare visitor to western Alaska and very rarely farther south.

Barn Swallow (Eurasian) – Hirundo rustica rustica group *

Barn Swallow (American) – Hirundo rustica erythrogaster *

Cliff Swallow – Petrochelidon pyrrhonota

Two subspecies groups differ in plumage, timing of breeding. More study is needed but these appear to be readily identifiable. ––Read more…

Cliff Swallow (Northern) – Petrochelidon pyrrhonota pyrrhonota group

Cliff Swallow (Mexican) – Petrochelidon pyrrhonota melanogaster

Cave Swallow – Petrochelidon fulva

Mexican and Caribbean groups differ on average in size and color, but variation is so great that it does not seem possible to identify a vagrant in the field with certainty. ––Read more…

Common House-Martin – Delichon urbicum

Family Paridae – Chickadees and Titmice

Carolina Chickadee – Poecile carolinensis

Black-capped Chickadee – Poecile atricapillus

Three general subspecies groups differ in plumage, but intergrade where ranges meet. Birds of the Pacific coast are most distinctive and might be reliably identifable.

Mountain Chickadee – Poecile gambeli

Two subspecies groups recently proposed for species status differ in DNA, but only slightly in plumage and proportions. Reliability of differences need to be determined but identification in the field will be difficult. ––Read more…

Mountain Chickadee (Interior West) – Poecile gambeli gambeli group

Mountain Chickadee (Pacific) – Poecile gambeli baileyae group

Mexican Chickadee – Poecile sclateri

Chestnut-backed Chickadee – Poecile rufescens

Two groups differ in plumage and are relatively distinctive. Intergrades occur in a limited area. ––Read more…

Chestnut-backed Chickadee (Northern) – Poecile rufescens rufescens

Chestnut-backed Chickadee (California) – Poecile rufescens barlowi group

Boreal Chickadee – Poecile hudsonicus

Two groups – Eastern (Brown-backed) and Western (Gray-backed) – can be distinguished by average plumage color, but the reliability of differences needs to be determined.

Gray-headed Chickadee – Poecile cinctus

Bridled Titmouse – Baeolophus wollweberi

Oak Titmouse – Baeolophus inornatus

Juniper Titmouse – Baeolophus ridgwayi

Tufted Titmouse – Baeolophus bicolor

Black-crested Titmouse – Baeolophus atricristatus

Family Remizidae – Verdin

Verdin – Auriparus flaviceps

Family Aegithalidae – Bushtit

Bushtit – Psaltriparus minimus

Two subspecies groups differ in plumage and are reliably distinguished in virtually all cases. The “Black-eared” Bushtit is merely a color morph of Interior subspecies, found mainly south of the US.

Bushtit (Pacific) – Psaltriparus minimus minimus group *

Bushtit (Interior West) – Psaltriparus minimus plumbeus [melanotis group] *

Family Sittidae – Nuthatches

Red-breasted Nuthatch – Sitta canadensis

White-breasted Nuthatch – Sitta carolinensis

Three subspecies groups differ in plumage, bill shape, and voice, and are reliably distinguishable in the field. Recent DNA studies reveal a fourth group in eastern Sierra Nevada, which needs clarification.

White-breasted Nuthatch (Eastern) – Sitta carolinensis carolinensis *

White-breasted Nuthatch (Rocky Mountain) – Sitta carolinensis mexicana group *

White-breasted Nuthatch (Pacific) – Sitta carolinensis aculeata group *

Pygmy Nuthatch – Sitta pygmaea

Three subspecies in North America differ in head color, flank color, and average size and might be identifiable in the field. Some California populations reportedly differ in voice. More study is needed.

Brown-headed Nuthatch – Sitta pusilla

Family Certhiidae – Creepers

Brown Creeper – Certhia americana

Four subspecies groups differ slightly in plumage and song. Recent studies reveal substantial differences in DNA, and suggest that at least the Mexican form (which is most distinctive in plumage and song and probably reliably identified in the field) should be split. ––Read more…

Brown Creeper (Pacific) – Certhia americana occidentalis group

Brown Creeper (Rocky Mountain) – Certhia americana montana group

Brown Creeper (Eastern) – Certhia americana americana group

Brown Creeper (Mexican) – Certhia americana albescens *

Family Troglodytidae – Wrens

Cactus Wren – Campylorhynchus brunneicapillus

Two subspecies groups differ in plumage and slightly in voice, and should be reliably distinguished in the field.

Cactus Wren (Mexican) – Campylorhynchus brunneicapillus anthonyi [brunneicapillus group] *

Cactus Wren (California) – Campylorhynchus brunneicapillus sandiegensis [affinis group] *

Rock Wren – Salpinctes obsoletus

Canyon Wren – Catherpes mexicanus

Sinaloa Wren – Thryothorus sinaloa

Carolina Wren – Thryothorus ludovicianus

Mexican population might be identifiable by plumage and song, but variation might be broadly clinal; more study is needed to assess differences and the extent of intergradation with Northern birds.

Bewick’s Wren – Thryomanes bewickii

Three subspecies groups differ in plumage, song, an DNA, but apparently intergrade where ranges meet.

Bewick’s Wren (Eastern) – Thryomanes bewickii bewickii group

Bewick’s Wren (Southwestern) – Thryomanes bewickii eremophilus [mexicanus group]

Bewick’s Wren (Pacific) – Thryomanes bewickii spilurus group

House Wren – Troglodytes aedon

The Mexican (Brown-throated) population might qualify as an identifiable form, but birds in the US are reportedly intergrades between the distinctive form farther south and US birds. Eastern and Western forms differ very slightly in plumage and voice but are probably not reliably identified in the field.

House Wren (Northern) – Troglodytes aedon aedon group

House Wren (Mexican or Brown-throated) – Troglodytes aedon cahooni

Winter Wren – Troglodytes hiemalis

Pacific Wren – Troglodytes pacificus

Alaskan populations differ in size and overall color, and extremes are probably identifiable but much of the variation is clinal.

Pacific Wren (Alaska) – Troglodytes pacificus alascensis group

Pacific Wren (Southern) – Troglodytes pacificus pacificus group

Sedge Wren – Cistothorus platensis

Marsh Wren – Cistothorus palustris

Eastern and Western populations differ substantially and consistently in song and singing behavior, and differ slightly in plumage and have been proposed for species status. In addition, Pacific birds differ at least in overall color from other Western birds, and a distinctively gray subspecies occurs in coastal southeast US.

Marsh Wren (Western) – Cistothorus palustris paludicola group *

Marsh Wren (Eastern) – Cistothorus palustris palustris group *

Family Polioptilidae – Gnatcatchers

Blue-gray Gnatcatcher – Polioptila caerulea

Two subspecies differ slightly in plumage and voice and might be reliably identified out of range, more study is needed.

Blue-gray Gnatcatcher (Eastern) – Polioptila caerulea caerulea

Blue-gray Gnatcatcher (Western) – Polioptila caerulea amoenissima [obscura group]

California Gnatcatcher – Polioptila californica

Black-tailed Gnatcatcher – Polioptila melanura

Eastern and Western forms are usually distinguishable by tail pattern, and more study might reveal other differences.

Black-tailed Gnatcatcher (Western or Sonoran) – Polioptila melanura lucida

Black-tailed Gnatcatcher (Eastern or Chihuahuan) – Polioptila melanura melanura

Black-capped Gnatcatcher – Polioptila nigriceps

Family Cinclidae – Dippers

American Dipper – Cinclus mexicanus

Family Pycnonotidae – Bulbuls

Red-whiskered Bulbul – Pycnonotus jocosus

Family Regulidae – Kinglets

Golden-crowned Kinglet – Regulus satrapa

Two subspecies groups differ consistently in plumage and should be reliably identifiable in the field (if they can be seen well enough…). Differences recently revealed in DNA of Brown Creeper, White-breasted Nuthatch, and Hairy Woodpecker suggest that Golden-crowned Kinglet might also comprise several distinctive forms. More study is needed!

Golden-crowned Kinglet (Western) – Regulus satrapa olivaceus group

Golden-crowned Kinglet (Eastern) – Regulus satrapa satrapa

Ruby-crowned Kinglet – Regulus calendula

Family Phylloscopidae – Leaf Warblers

Willow Warbler – Phylloscopus trochilus

Wood Warbler – Phylloscopus sibilatrix

Dusky Warbler – Phylloscopus fuscatus

Pallas’s Leaf-Warbler – Phylloscopus proregulus

Yellow-browed Warbler – Phylloscopus inornatus

Arctic Warbler – Phylloscopus borealis

Recent research using DNA and song recommends splitting Arctic Warbler into three species. Alaska breeders keep their current name, and Kamchatka Leaf Warbler Phylloscopus examinandus is added to the North American list, as the subspecies xanthodryas is a rare visitor to the Western Aleutians. A third species breeds in Japan and has not been recorded in North America. Field identification of non-singing birds needs to be worked out.

Arctic Warbler (Northern) – Phylloscopus borealis borealis *

Arctic Warbler (Kamchatka Leaf Warbler) – Phylloscopus borealis xanthodryas *

Family Sylviidae

Lesser Whitethroat – Sylvia curruca

Wrentit – Chamaea fasciata

Family Acrocephalidae

Sedge Warbler – Acrocephalus schoenobaenus

Family Megaluridae

Lanceolated Warbler – Locustella lanceolata

Middendorff’s Grasshopper-Warbler – Locustella ochotensis

Family Muscicapidae – Old World Flycatchers

Spotted Flycatcher – Muscicapa striata

Dark-sided Flycatcher – Muscicapa sibirica

Gray-streaked Flycatcher – Muscicapa griseisticta

Asian Brown Flycatcher – Muscicapa dauurica

Narcissus Flycatcher – Ficedula narcissina

Taiga Flycatcher – Ficedula albicilla

Family Turdidae – Thrushes

Rufous-tailed Robin – Luscinia sibilans

Siberian Rubythroat – Luscinia calliope

Bluethroat – Luscinia svecica

Siberian Blue Robin – Luscinia cyane

Red-flanked Bluetail – Tarsiger cyanurus

Northern Wheatear – Oenanthe oenanthe

Alaskan and Greenland breeders differ in average size and overall color, but identification in the field is tenuous at best.

Stonechat – Saxicola torquatus

Eastern Bluebird – Sialia sialis

Differences in two subspecies groups are slight, despite disjunct range, perhaps not identifiable out of range, but more study is warranted.

Eastern Bluebird (Eastern) – Sialia sialis sialis group

Eastern Bluebird (Mexican) – Sialia sialis fulva [guatemalae group]

Western Bluebird – Sialia mexicana

Mountain Bluebird – Sialia currucoides

Townsend’s Solitaire – Myadestes townsendi

Brown-backed Solitaire – Myadestes occidentalis

Orange-billed Nightingale-Thrush – Catharus aurantiirostris

Black-headed Nightingale-Thrush – Catharus mexicanus

Veery – Catharus fuscescens

Subspecies show only slight and average differences in overall color and are not safely identified in the field.

Gray-cheeked Thrush – Catharus minimus

Bicknell’s Thrush – Catharus bicknelli

Swainson’s Thrush – Catharus ustulatus

Two subspecies groups differ consistently in plumage and slightly in song, also have different winter range and migration timing. These should be reliably identifiable in the field, but extent of any intergradation needs to be determined, and the Western Mountain populations (appearance like Taiga birds) need to be studied.

Swainson’s Thrush (Pacific or Russet-backed) – Catharus ustulatus ustulatus group *

Swainson’s Thrush (Taiga or Olive-backed) – Catharus ustulatus swainsoni *

Hermit Thrush – Catharus guttatus

Three subspecies groups reliably distinguished in the field by plumage, size, and voice. Some intermediate populations make identification more challenging, but most individuals should be relatively easy to classify.

Hermit Thrush (Pacific) – Catharus guttatus guttatus group *

Hermit Thrush (Interior West) – Catharus guttatus auduboni group *

Hermit Thrush (Taiga) – Catharus guttatus faxoni group *

Wood Thrush – Hylocichla mustelina

Eurasian Blackbird – Turdus merula

Eyebrowed Thrush – Turdus obscurus

Dusky Thrush – Turdus eunomus

Naumann’s Thrush – Turdus naumanni

Fieldfare – Turdus pilaris

Redwing – Turdus iliacus

Song Thrush – Turdus philomelos

Clay-colored Thrush – Turdus grayi

White-throated Thrush – Turdus assimilis

Rufous-backed Robin – Turdus rufopalliatus

American Robin – Turdus migratorius

Variation is slight and clinal, with much overlap, and no subspecies are reliably identifiable. ––Read more…

Varied Thrush – Ixoreus naevius

Aztec Thrush – Ridgwayia pinicola

Family Mimidae – Mockingbirds and Thrashers

Gray Catbird – Dumetella carolinensis

Northern Mockingbird – Mimus polyglottos

Bahama Mockingbird – Mimus gundlachii

Sage Thrasher – Oreoscoptes montanus

Brown Thrasher – Toxostoma rufum

Long-billed Thrasher – Toxostoma longirostre

Bendire’s Thrasher – Toxostoma bendirei

Curve-billed Thrasher – Toxostoma curvirostre

Two subspecies groups differ in plumage and DNA, and slightly in voice. Most should be reliably identified, but some conflicting evidence in the contact zone gives reason for caution. ––Read more…

Curve-billed Thrasher (Texas or Chihuahuan) – Toxostoma curvirostre curvirostre group *

Curve-billed Thrasher (Arizona or Sonoran or Palmer’s) – Toxostoma curvirostre palmeri group *

California Thrasher – Toxostoma redivivum

Crissal Thrasher – Toxostoma crissale

Le Conte’s Thrasher – Toxostoma lecontei

Blue Mockingbird – Melanotis caerulescens

Family Sturnidae – Starlings and Mynas

Common Hill Myna – Gracula religiosa

Common Myna – Acridotheres tristis

European Starling – Sturnus vulgaris

Family Prunellidae – Accentors

Siberian Accentor – Prunella montanella

Family Motacillidae – Wagtails and Pipits

Eastern Yellow Wagtail – Motacilla tschutschensis

Two subspecies (Kamchatka a rare visitor to western Alaska) differ in plumage and many/most are probably reliably separated in adult male plumage, but intergradation and variation need to be assessed. Some authorities split these into two species.

Eastern Yellow Wagtail (Siberian) – Motacilla tschutschensis tschutschensis

Eastern Yellow Wagtail (Kamchatka) – Motacilla tschutschensis simillima

Citrine Wagtail – Motacilla citreola

Gray Wagtail – Motacilla cinerea

White Wagtail – Motacilla alba

Three subspecies groups all reliably distinguished in the field (although Black-backed and Siberian are barely distinguishable from each other in non-adult-male plumages). Only Siberian occurs regularly in North America.

White Wagtail (European) – Motacilla alba alba group

White Wagtail (Siberian) – Motacilla alba ocularis

White Wagtail (Black-backed ) – Motacilla alba lugens

Tree Pipit – Anthus trivialis

Olive-backed Pipit – Anthus hodgsoni

Pechora Pipit – Anthus gustavi

Red-throated Pipit – Anthus cervinus

American Pipit – Anthus rubescens

Two subspecies groups more or less reliably distinguished. Although both are quite variable and there is overlap in all identifying characteristics, the sum of differences makes most Asian birds readily distinguishable from American.

American Pipit (Asian) – Anthus rubescens japonicus

American Pipit (Buff-bellied Pipit) – Anthus rubescens rubescens group

Sprague’s Pipit – Anthus spragueii

Family Bombycillidae – Waxwings

Bohemian Waxwing – Bombycilla garrulus

Two subspecies (Asian a very rare visitor) should be reliably distinguished by plumage, although differences involve merely saturation of colors and not pattern, so identifying a bird far out-of-range might be tenuous.

Bohemian Waxwing (American) – Bombycilla garrulus pallidiceps

Bohemian Waxwing (Asian) – Bombycilla garrulus centralasiae

Cedar Waxwing – Bombycilla cedrorum

Family Ptilogonatidae – Silky-Flycatchers

Gray Silky-flycatcher – Ptilogonys cinereus

Phainopepla – Phainopepla nitens

Family Peucedramidae – Olive Warbler

Olive Warbler – Peucedramus taeniatus

Family Calcariidae – Longspurs

McCown’s Longspur – Rhynchophanes mccownii

Lapland Longspur – Calcarius lapponicus

Smith’s Longspur – Calcarius pictus

Chestnut-collared Longspur – Calcarius ornatus

Snow Bunting – Plectrophenax nivalis

Subspecies townsendi of western Alaska averages larger and whiter than widespread nivalis, but differences are probably not sufficient to allow identification, and intergrades occur.

McKay’s Bunting – Plectrophenax hyperboreus

Family Parulidae – Wood Warblers

Blue-winged Warbler – Vermivora cyanoptera

Golden-winged Warbler – Vermivora chrysoptera

Tennessee Warbler – Oreothlypis peregrina

Orange-crowned Warbler – Oreothlypis celata

Four subspecies groups may sometimes be distinguishable in the field. It may be possible to identify at least Pacific (V. c. lutescens) with certainty in the field, but differences are small and need clarification.

Orange-crowned Warbler (Taiga) – Vermivora celata celata

Orange-crowned Warbler (Interior West ) – Vermivora celata orestera

Orange-crowned Warbler (Pacific) – Vermivora celata lutescens

Orange-crowned Warbler (Channel Islands ) – Vermivora celata sordida

Nashville Warbler – Oreothlypis ruficapilla

Differences in song, plumage, and possibly tail movements (as well as DNA) between eastern and western populations may be sufficient for field identification, but this has not yet been confirmed.

Nashville Warbler (Eastern) – Vermivora ruficapilla ruficapilla

Nashville Warbler (Western or Calaveras) – Vermivora ruficapilla ridgwayi

Virginia’s Warbler – Oreothlypis virginiae

Colima Warbler – Oreothlypis crissalis

Lucy’s Warbler – Oreothlypis luciae

Crescent-chested Warbler – Parula superciliosa

Northern Parula – Parula americana

Subtle differences in song between Eastern and Western populations of this species are probably not reliable enough to allow confident identification.

Tropical Parula – Parula pitiayumi

Yellow Warbler – Dendroica petechia

Three major groups are distinctive. Within the Northern group it is often possible to identify migrants as belonging to, for example, a northern population based on drab color and/or timing of migration, but this is not enough to allow a subspecies label. Golden and Mangrove populations are both distinctive and identifiable.

Yellow Warbler (Northern) – Dendroica petechia aestiva group *

Yellow Warbler (Mangrove) – Dendroica petechia erithachorides group *

Yellow Warbler (Golden) – Dendroica petechia gundlachi [petechia group] *

Chestnut-sided Warbler – Dendroica pensylvanica

Magnolia Warbler – Dendroica magnolia

Cape May Warbler – Dendroica tigrina

Black-throated Blue Warbler – Dendroica caerulescens

Two populations (Northern and Appalachian) differ on average in adult male plumage, but extensive intergradation and variation makes this difference almost meaningless.

Yellow-rumped Warbler – Dendroica coronata

Two populations often considered separate species; identifiable in all plumages by multiple features, as well as by call note. Audubon’s includes two other distinctive forms south of the US and might be split further.

Yellow-rumped Warbler (Myrtle or Taiga) – Dendroica coronata coronata group *

Yellow-rumped Warbler (Audubon’s or Western) – Dendroica coronata auduboni group *

Black-throated Gray Warbler – Dendroica nigrescens

A substantial difference in DNA between coastal and interior populations, but no known difference in plumage or voice. More study is warranted.

Golden-cheeked Warbler – Dendroica chrysoparia

Black-throated Green Warbler – Dendroica virens

Townsend’s Warbler – Dendroica townsendi

Hermit Warbler – Dendroica occidentalis

Blackburnian Warbler – Dendroica fusca

Yellow-throated Warbler – Dendroica dominica

Coastal and Interior forms differ slightly in plumage and bill length, but extensive variation makes identification of many birds uncertain. An extralimital population in the Bahamas has recently been elevated to species status.

Grace’s Warbler – Dendroica graciae

Pine Warbler – Dendroica pinus

Kirtland’s Warbler – Dendroica kirtlandii

Prairie Warbler – Dendroica discolor

Northern and Florida populations differ slightly in plumage color and have no overlap in breeding range. Currently not considered field identifiable but more study is warranted.

Palm Warbler – Dendroica palmarum

Two populations nearly always distinguishable by overall color.

Palm Warbler (Brown) – Dendroica palmarum palmarum

Palm Warbler (Yellow) – Dendroica palmarum hypochrysea

Bay-breasted Warbler – Dendroica castanea

Blackpoll Warbler – Dendroica striata

Cerulean Warbler – Dendroica cerulea

Black-and-white Warbler – Mniotilta varia

American Redstart – Setophaga ruticilla

Prothonotary Warbler – Protonotaria citrea

Worm-eating Warbler – Helmitheros vermivorum

Swainson’s Warbler – Limnothlypis swainsonii

Ovenbird – Seiurus aurocapilla

Northern Waterthrush – Parkesia noveboracensis

Louisiana Waterthrush – Parkesia motacilla

Kentucky Warbler – Oporornis formosus

Connecticut Warbler – Oporornis agilis

Mourning Warbler – Oporornis philadelphia

MacGillivray’s Warbler – Oporornis tolmiei

Common Yellowthroat – Geothlypis trichas

Several identifiable forms must be contained within Common Yellowthroat. A rough grouping is listed here, but more study is needed to sort out differences in plumage and song.

Common Yellowthroat (Pacific) – Geothlypis trichas arizela group

Common Yellowthroat (Interior West) – Geothlypis trichas occidentalis group

Common Yellowthroat (Eastern) – Geothlypis trichas trichas group

Common Yellowthroat (Southwestern) – Geothlypis trichas chryseola group

Bahama Yellowthroat – Geothlypis rostrata

Gray-crowned Yellowthroat – Geothlypis poliocephala

Hooded Warbler – Wilsonia citrina

Wilson’s Warbler – Wilsonia pusilla

Pacific and Taiga forms differ enough in plumage and perhaps voice to be recognizable, although many intergrades and an intermediate population (W. p. pileolata in the Interior West cloud the issue.

Wilson’s Warbler (Taiga) – Wilsonia pusilla pusilla

Wilson’s Warbler (Pacific) – Wilsonia pusilla chryseola

Canada Warbler – Wilsonia canadensis

Red-faced Warbler – Cardellina rubrifrons

Painted Redstart – Myioborus pictus

Slate-throated Redstart – Myioborus miniatus

Fan-tailed Warbler – Euthlypis lachrymosa

Golden-crowned Warbler – Basileuterus culicivorus

Rufous-capped Warbler – Basileuterus rufifrons

Eastern and Western Mexican subspecies differ slightly in plumage and might be reliably identifiable.

Yellow-breasted Chat – Icteria virens

Family Genus Incertae Sedis (Bananaquit)

Bananaquit – Coereba flaveola

Family Thraupidae – Tanagers

Western Spindalis – Spindalis zena

Two subspecies from the Bahamas are reliably distinguished by adult male plumage and have been recorded in Florida. Another subspecies from Cuba may also occur.

Western Spindalis (Southern Bahamas or Green-backed) – Spindalis zena zena

Western Spindalis (Northern Bahamas or Black-backed) – Spindalis zena townsendi

Western Spindalis (Cuban) – Spindalis zena pretrei

Red-legged Honeycreeper – Cyanerpes cyaneus

Family Emberizidae – New World Sparrows

White-collared Seedeater – Sporophila torqueola

The bright Cinnamon-rumped form from West Mexico has been recorded several times from California, Arizona, and Texas. All are suspected of being escapes but regardless of that males are easily identifiable in the field.

White-collared Seedeater (East Mexican) – Sporophila torqueola morelleti group

White-collared Seedeater (Cinnamon-rumped or West Mexican) – Sporophila torqueola torqueola

Yellow-faced Grassquit – Tiaris olivaceus

Black-faced Grassquit – Tiaris bicolor

Olive Sparrow – Arremonops rufivirgatus

Green-tailed Towhee – Pipilo chlorurus

Spotted Towhee – Pipilo maculatus

Three subspecies groups differ in plumage and voice, but plumage, song, and call seem to vary independently to some extent, and this arrangement is certainly not the best. More study is needed.

Spotted Towhee (Pacific) – Pipilo maculatus oregonus group

Spotted Towhee (Great Plains) – Pipilo maculatus arcticus group

Spotted Towhee (Southwestern) – Pipilo maculatus montanus group

Eastern Towhee – Pipilo erythrophthalmus

Populations in the southeast differ from northern birds in eye color and slightly in plumage, but intergrade broadly so that variation is mostly clinal.

Canyon Towhee – Melozone fusca

California Towhee – Melozone crissalis

Abert’s Towhee – Melozone aberti

Rufous-winged Sparrow – Peucaea carpalis

Cassin’s Sparrow – Peucaea cassinii

Bachman’s Sparrow – Peucaea aestivalis

Variation in upperparts color are fairly obvious, but clinal, and it is doubtful that any of the three subspecies could be reliably identified out of range.

Botteri’s Sparrow – Peucaea botterii

Two subspecies differ fairly strongly in upperparts color, and would probably be identifiable out of range. No other differences are known.

Botteri’s Sparrow (Western) – Peucaea botterii arizonae

Botteri’s Sparrow (Eastern) – Peucaea botterii texana

Rufous-crowned Sparrow – Aimophila ruficeps

Two subspecies groups differ slightly in plumage and size. Most are probably reliably identified in the field but more study is needed.

Rufous-crowned Sparrow (Pacific) – Aimophila ruficeps ruficeps group

Rufous-crowned Sparrow (Interior) – Aimophila ruficeps scottii group

Five-striped Sparrow – Amphispiza quinquestriata

American Tree Sparrow – Spizella arborea

Chipping Sparrow – Spizella passerina

Clay-colored Sparrow – Spizella pallida

Brewer’s Sparrow – Spizella breweri

Two subspecies differ on average in plumage and size, slightly in song and DNA. Often proposed for species status, the field identification of these two forms still remains to be worked out.

Brewer’s Sparrow (Southern) – Spizella breweri breweri *

Brewer’s Sparrow (Timberline) – Spizella breweri taverneri *

Field Sparrow – Spizella pusilla

Worthen’s Sparrow – Spizella wortheni

Black-chinned Sparrow – Spizella atrogularis

Vesper Sparrow – Pooecetes gramineus

Lark Sparrow – Chondestes grammacus

Black-throated Sparrow – Amphispiza bilineata

Two subspecies groups (Western and Texas) differ slightly in overall color, tail pattern, and size, but more study is needed to clarify potential differences.

Sage Sparrow – Amphispiza belli

Two subspecies groups differ consistently in plumage and song and are reliably identified in the field.

Sage Sparrow (Pacific or Bell’s) – Amphispiza belli belli group *

Sage Sparrow (Interior) – Amphispiza belli nevadensis *

Lark Bunting – Calamospiza melanocorys

Savannah Sparrow – Passerculus sandwichensis

Widespread Continental forms vary slightly in plumage and size, but are generally not distinguishable from each other in the field. Ipswich, Belding’s, and Large-billed are all reliably identified, although intermediate populations and/or intergrades cloud the issue. In addition to plumage, differences in bill size, crown shape, and timing of breeding are useful. ––Read more…

Savannah Sparrow (Ipswich) – Passerculus sandwichensis princeps *

Savannah Sparrow (Continental) – Passerculus sandwichensis sandwichensis group *

Savannah Sparrow (Belding’s) – Passerculus sandwichensis beldingi [guttatus group] *

Savannah Sparrow (Large-billed) – Passerculus sandwichensis rostratus group *

Grasshopper Sparrow – Ammodramus savannarum

Four subspecies. Differences in plumage might allow confident identification of some individuals in the field, but on current knowledge none are considered identifiable.

Baird’s Sparrow – Ammodramus bairdii

Henslow’s Sparrow – Ammodramus henslowii

Le Conte’s Sparrow – Ammodramus leconteii

Nelson’s Sparrow – Ammodramus nelsoni

Two subspecies groups differ consistently in plumage and are reliably identified.

Nelson’s Sparrow (Interior) – Ammodramus nelsoni nelsoni group *

Nelson’s Sparrow (Atlantic or Acadian) – Ammodramus nelsoni subvirgatus *

Saltmarsh Sparrow – Ammodramus caudacutus

Seaside Sparrow – Ammodramus maritimus

Three subspecies groups differ in plumage and are probably reliably identifiable in the field, although considerable variation and multiple subspecies within both Atlantic and Gulf Coast populations might complicate identification. The distinctive Dusky Seaside Sparrow is extinct.

Seaside Sparrow (Atlantic) – Ammodramus maritimus maritimus group

Seaside Sparrow (Dusky) – Ammodramus maritimus nigrescens

Seaside Sparrow (Gulf Coast) – Ammodramus maritimus sennetti group

Seaside Sparrow (Cape Sable) – Ammodramus maritimus mirabilis

Fox Sparrow – Passerella iliaca

Four subspecies groups distinguished by plumage, song, calls, and in some cases by size and bill shape. The presence of limited intermediate populations and interbreeding does not affect the ease with which the vast majority of Fox Sparrows can be identified to subspecies group.

Fox Sparrow (Sooty or Pacific) – Passerella iliaca unalaschcensis group *

Fox Sparrow (Thick-billed or California) – Passerella iliaca megarhyncha group *

Fox Sparrow (Slate-colored or Interior West) – Passerella iliaca schistacea group *

Fox Sparrow (Red or Taiga) – Passerella iliaca iliaca group *

Song Sparrow – Melospiza melodia

Extensive variation across its wide range can be partitioned loosely into the forms listed here, but variation is mostly clinal and all forms intergrade. Similar to Horned Lark and others, there are certainly better ways to subdivide the species, but more study is needed.

Song Sparrow (Aleutian) – Melospiza melodia sanaka group

Song Sparrow (Pacific Northwest) – Melospiza melodia rufina group

Song Sparrow (California) – Melospiza melodia samuelis group

Song Sparrow (Southwestern) – Melospiza melodia fallax group

Song Sparrow (Eastern) – Melospiza melodia melodia group

Lincoln’s Sparrow – Melospiza lincolnii

Swamp Sparrow – Melospiza georgiana

Subspecies nigrescens on mid-Atlantic coast might be identifiable, at least in breeding plumage, but subtle differences in plumage require testing.

White-throated Sparrow – Zonotrichia albicollis

Harris’s Sparrow – Zonotrichia querula

White-crowned Sparrow – Zonotrichia leucophrys

Best considered three identifiable forms, with Taiga group including pale-lored birds in the west and dark-lored in the east. Pacific is distinctive and always readily identifiable. Mountain and Taiga intergrade across a broad area, and Mountain is very similar to Eastern Taiga birds, but most should be identifiable by plumage and voice. ––Read more…

White-crowned Sparrow (Taiga or Gambel’s) – Zonotrichia leucophrys leucophrys group

White-crowned Sparrow (Mountain) – Zonotrichia leucophrys oriantha

White-crowned Sparrow (Pacific or Nuttall’s) – Zonotrichia leucophrys nuttalli group

Golden-crowned Sparrow – Zonotrichia atricapilla

Dark-eyed Junco – Junco hyemalis

Six forms can be identified with confidence in the field, even though intergrades occur wherever ranges overlap. A broad intergrade zone between Slate-colored and Oregon in the Canadian Rockies produces a variable population, while farther north and west an apparently stable intermediate form is found which could be listed as a seventh identifiable population. More study is needed to clarify extent of intergradation and slight differences in songs and calls.

Dark-eyed Junco (Slate-colored ) – Junco hyemalis hyemalis group

Dark-eyed Junco (Oregon) – Junco hyemalis oreganus group

Dark-eyed Junco (Pink-sided) – Junco hyemalis mearnsi

Dark-eyed Junco (White-winged) – Junco hyemalis aikeni

Dark-eyed Junco (Gray-headed) – Junco hyemalis caniceps

Dark-eyed Junco (Red-backed) – Junco hyemalis dorsalis

Yellow-eyed Junco – Junco phaeonotus

Pine Bunting – Emberiza leucocephalos

Yellow-browed Bunting – Emberiza chrysophrys

Little Bunting – Emberiza pusilla

Rustic Bunting – Emberiza rustica

Yellow-throated Bunting – Emberiza elegans

Yellow-breasted Bunting – Emberiza aureola

Gray Bunting – Emberiza variabilis

Pallas’s Bunting – Emberiza pallasi

Reed Bunting – Emberiza schoeniclus

Family Cardinalidae – Cardinals and Buntings

Hepatic Tanager – Piranga flava

Summer Tanager – Piranga rubra

Two subspecies might be distinguished in the field by bill size and plumage color; more study is needed.

Summer Tanager (Western or Cooper’s) – Piranga rubra cooperi group

Summer Tanager (Eastern) – Piranga rubra rubra

Scarlet Tanager – Piranga olivacea

Western Tanager – Piranga ludoviciana

Flame-colored Tanager – Piranga bidentata

Two subspecies probably occur (West Mexican a rare visitor to Arizona, East Mexican form possibly a rare visitor to Texas, but this needs confirmation). Adult males and possibly adult females are fairly distinctive based on plumage color.

Flame-colored Tanager (West Mexican) – Piranga bidentata bidentata

Flame-colored Tanager (East Mexican) – Piranga bidentata sanguinolenta

Crimson-collared Grosbeak – Rhodothraupis celaeno

Northern Cardinal – Cardinalis cardinalis

Two subspecies groups are reliably distinguished by bill shape and plumage pattern.

Northern Cardinal (Southwestern) – Cardinalis cardinalis superbus group

Northern Cardinal (Eastern) – Cardinalis cardinalis cardinalis group

Pyrrhuloxia – Cardinalis sinuatus

Yellow Grosbeak – Pheucticus chrysopeplus

Rose-breasted Grosbeak – Pheucticus ludovicianus

Black-headed Grosbeak – Pheucticus melanocephalus

Blue Bunting – Cyanocompsa parellina

Blue Grosbeak – Passerina caerulea

Lazuli Bunting – Passerina amoena

Indigo Bunting – Passerina cyanea

Varied Bunting – Passerina versicolor

Painted Bunting – Passerina ciris

Dickcissel – Spiza americana

Family Icteridae – Orioles and Blackbirds

Bobolink – Dolichonyx oryzivorus

Red-winged Blackbird – Agelaius phoeniceus

Two subspecies groups represent extremes of variation and are reliably distinguished by plumage and differ slightly in song, but intermediate populations exist. Populations in southern Florida may differ in song and plumage and deserve more study.

Red-winged Blackbird (Typical) – Agelaius phoeniceus phoeniceus group

Red-winged Blackbird (Bicolored) – Agelaius phoeniceus californicus group

Tricolored Blackbird – Agelaius tricolor

Tawny-shouldered Blackbird – Agelaius humeralis

Eastern Meadowlark – Sturnella magna

Two subspecies groups can apparently be distinguished by plumage color and voice, although identifying either within the range of the other would be extremely difficult.

Eastern Meadowlark (Eastern) – Sturnella magna magna group

Eastern Meadowlark (Lilian’s) – Sturnella magna lilianae

Western Meadowlark – Sturnella neglecta

Yellow-headed Blackbird – Xanthocephalus xanthocephalus

Rusty Blackbird – Euphagus carolinus

Brewer’s Blackbird – Euphagus cyanocephalus

Common Grackle – Quiscalus quiscula

Two subspecies groups are reliably identified in adult male plumage, somewhat less distinctive in females. Many intergrades occur in a relatively narrow band where ranges meet from Louisiana to New England.

Common Grackle (Purple) – Quiscalus quiscula quiscula group

Common Grackle (Bronzed) – Quiscalus quiscula versicolor

Boat-tailed Grackle – Quiscalus major

Iris color varies regionally, but no other significant differences are known.

Great-tailed Grackle – Quiscalus mexicanus

Populations west of southeastern Arizona differ slightly in size, female plumage color, and possibly voice, and differ significantly in DNA, from birds farther east. These may be identifiable (they have even been suggested as possible species) but more study is needed to work out identification criteria and to assess an apparent contact zone in southeastern Arizona.

Shiny Cowbird – Molothrus bonariensis

Bronzed Cowbird – Molothrus aeneus

Eastern and Western populations are quite different in female plumage, and several flight call variations are also known. More study is needed to sort out differences.

Bronzed Cowbird (Western) – Molothrus aeneus loyei group

Bronzed Cowbird (Eastern) – Molothrus aeneus aeneus

Brown-headed Cowbird – Molothrus ater

Differences in flight calls and in gape color of juveniles might allow identification of subspecies. More study is needed.

Brown-headed Cowbird (Western) – Molothrus ater artemisiae group

Brown-headed Cowbird (Eastern) – Molothrus ater ater

Black-vented Oriole – Icterus wagleri

Orchard Oriole – Icterus spurius

The East Mexican form (Fuertes’s Oriole) is very distinctive in adult male plumage, recorded once in Texas. Sometimes considered a distinct species.

Orchard Oriole (Northern) – Icterus spurius spurius

Orchard Oriole (Fuertes’s) – Icterus spurius fuertesi

Hooded Oriole – Icterus cucullatus

Eastern and Western populations differ in intensity of male plumage, but intergrade broadly and, given the variation shown in carotenoid pigments in plumage of birds, are probably not safely identified by this feature alone.

Streak-backed Oriole – Icterus pustulatus

Bullock’s Oriole – Icterus bullockii

Spot-breasted Oriole – Icterus pectoralis

Altamira Oriole – Icterus gularis

Audubon’s Oriole – Icterus graduacauda

Baltimore Oriole – Icterus galbula

Scott’s Oriole – Icterus parisorum

Family Fringillidae – Finches

Common Chaffinch – Fringilla coelebs

Brambling – Fringilla montifringilla

Gray-crowned Rosy-Finch – Leucosticte tephrocotis

Four subspecies groups are identifiable by plumage and size. Listed here as four groups, but these could also be sorted into two groups: Gray-cheeked (Bering Sea, Aleutian, and Coastal) and Brown-cheeked (Interior).

Gray-crowned Rosy-Finch (Bering Sea ) – Leucosticte tephrocotis umbrina

Gray-crowned Rosy-Finch (Aleutian) – Leucosticte tephrocotis griseonucha

Gray-crowned Rosy-Finch (Gray-cheeked or Hepburn’s or Coastal) – Leucosticte tephrocotis littoralis

Gray-crowned Rosy-Finch (Interior) – Leucosticte tephrocotis tephrocotis group

Black Rosy-Finch – Leucosticte atrata

Brown-capped Rosy-Finch – Leucosticte australis

Pine Grosbeak – Pinicola enucleator

Several subspecies groups are identifiable by plumage, size and flight call, but more study is needed to sort out variation and assess intermediate populations. Kamchatka subspecies recorded several times in western Alaska differs substantially from North American populations in DNA barcode test.

Pine Grosbeak (Kamchatka) – Pinicola enucleator kamtschatkensis

Pine Grosbeak (Pacific) – Pinicola enucleator flammula group

Pine Grosbeak (Interior West) – Pinicola enucleator montana group

Pine Grosbeak (Taiga) – Pinicola enucleator leucura group

Common Rosefinch – Carpodacus erythrinus

Purple Finch – Carpodacus purpureus

Two subspecies are nearly always distinguishable by plumage, structure, and voice, with limited intergradation. ––Read more…

Purple Finch (Eastern) – Carpodacus purpureus purpureus *

Purple Finch (California) – Carpodacus purpureus californicus *

Cassin’s Finch – Carpodacus cassinii

House Finch – Carpodacus mexicanus

Oriental Greenfinch – Chloris sinica

Red Crossbill – Loxia curvirostra

Ten different call types now known and nearly always identifiable by analysis of recordings, also differ very slightly in bill size and shape. ––Read more…

White-winged Crossbill – Loxia leucoptera

Common Redpoll – Acanthis flammea

Two subspecies distinguishable by size and average differences in color. Most are probably safely identified, although these subspecies are quite poorly-known. ––Read more…

Common Redpoll (Southern) – Acanthis flammea flammea

Common Redpoll (Greater or Greenland) – Acanthis flammea rostrata

Hoary Redpoll – Acanthis hornemanni

Two subspecies distinguishable by size and average difference in color. Most are probably safely identified, although these subspecies are quite poorly-known. ––Read more…

Hoary Redpoll (Southern) – Acanthis hornemanni exilipes

Hoary Redpoll (Hornemann’s or Greenland) – Acanthis hornemanni hornemanni

Eurasian Siskin – Spinus spinus

Pine Siskin – Spinus pinus

Lesser Goldfinch – Spinus psaltria

Adult males occur in two distinctive forms – Black-backed and Green-backed – that show strong geographic basis, but variation and the occurrence of each type well within the range of the other suggests that this color difference represents a morph rather than a subspecific difference.

Lawrence’s Goldfinch – Spinus lawrencei

American Goldfinch – Spinus tristis

Eastern and Western (and perhaps Pacific) forms differ slightly in plumage and possibly voice. These are probably not safely identified in the field but more study is warranted.

Eurasian Bullfinch – Pyrrhula pyrrhula

Evening Grosbeak – Coccothraustes vespertinus

Four forms are distinguishable by flight calls, more or less matching named subspecies, but more study is needed to clarify differences and to match vocal types with plumage and bill size variation.

Hawfinch – Coccothraustes coccothraustes

Family Passeridae – Old World Sparrows

House Sparrow – Passer domesticus

Eurasian Tree Sparrow – Passer montanus

Family Estrildidae – Waxbills, Munias, and allies

Nutmeg Mannikin – Lonchura punctulata

37 thoughts on “Field Identifiable Subspecies of birds – an annotated list”

  1. Isn’t the Hepburn’s Gray-crowned Rosy-Finch the coastal group? What about grouping them by overall plumage color (brownish/blackish) rather than cheek color?

    eBird and Clements suggest the name Woodhouse’s Western Scrub-Jay for the interior groups based on the latin trinomial.

    From what I’ve read (and also eBird and Clements) the Northern Pygmy-Owl subspecies G. g. gnoma is already referred to as the Mountain Pgymy-Owl, Not Mexican. But Mexican sounds better and more exotic and is probably more accurate.

    1. Thanks Matt, I’ve updated English names on these. It’s too bad if gnoma has acquired the name “Mountain Pygmy-Owl” because it barely enters the US in Arizona, and the subspecies pinicola is found widely in the mountain west and might differ enough in voice to be recognizable as well.

  2. You left out (maybe intentionally?) waynei Black-throated Green Warblers. Their breeding range (coastal Carolinas and Virginia) is completely different than the nominate ssp and having held skins in my hand, they appear to be identifiable in the field.

    In the past I did a small bit of work for a study looking to get some morphometric data determining precisely what the difference was between a typical virens and a typical waynei, and in the measurements I was taking it appeared that the birds identifiable as waynei are smaller, slighter billed, and with significantly less black on the flanks.

    I never heard what became of that particular data, but it might be one to add to your list.

    1. Thanks Nate. I hadn’t even considered Wayne’s Black-throated Green, but I will definitely check it out.
      And this gives me an opportunity to discuss an inconsistency of subspecies treatment that I’ve wanted to bring up. When naming these identifiable subspecies I tend to “reward” species with limited variation, and “punish” complexity. I’ll use Snow Goose as an example, as it’s a species that I know and that has a pattern of variation similar to Black-throated Green. The Snow Goose is almost uniform in appearance over a wide range, and has one disjunct breeding population (Greater Snow Goose) which looks slightly different. That earned it a place on my list. At the same time I lumped most of the variation in Canada Goose, because there are a lot of different populations varying in size and color, making identification of one individual bird extremely difficult. I think that’s a byproduct of this particular approach to categorizing subspecies, but it also shows up throughout bird taxonomy. I think it has a lot to do with the widespread resistance to the idea of ten species of Red Crossbills. I believe there would be a lot more support for Crossbill splitting if it was only into two or three species.

  3. Surely Buff-bellied Pipit (as used in Europe and Asia for both subspecies) is a better English name than ‘Asian American Pipit’ for Anthus rubescens japonicus?!

    1. I agree. I cringed a little when this name came up, but I am using the official AOU names for species. Hopefully they will change this name soon, because as it stands it doesn’t work for a substantial portion of the species’ range, and birders in Asia are not going to call their pipits “American”. For now it has to be American Pipit, which means that any regional name like Asian or Siberian will be nonsensical.

  4. I’m curious to see Black-backed Oriole on this list. Is there a US record for this species? I don’t see it mentioned for the US in either the AOU nor ABA lists.

    Also, I’m a bit surprised not to see any mention of a few subspecies (and groups) which I thought were relatively field-identifiable. Most notably:
    Scaled Quail (Texan castanogastris vs. the rest)
    Wrentit (northern vs. southern groups)
    Bachman’s Sparrow (illinoiensis vs. the rest)
    Botteri’s Sparrow (arizonae vs. texana)
    Great-tailed Grackle (nelsoni vs. rest: probably two species here!)
    I suppose clinality may obscure the first four cases enough that they may not make the cut, but the last seems to be a pretty solid one. Size, female plumage characters, and voice (especially) all can identify nelsoni Great-tails. A recent molecular phylogeny [Powell et al. 2008. Condor 110(4):718-728] even suggests that they are not sister to the rest of the Great-tailed complex, but are more closely related to the extinct Slender-billed Grackle of the Rio Lerma marshes of DF Mexico.

    1. Hi Dan, Thanks very much for these comments. There is a Black-backed Oriole record in San Diego, CA, (presumably one individual, seen off-and-on from 2000 to 2002) but you are correct that it hasn’t been accepted by any records committee and I will remove it from this list.

      I debated including some of those other species, especially Botteri’s Sparrow and Great-tailed Grackle. My concern about the grackle is that Phillips (1964) described the secondary contact in Arizona in the 1940s and 50s, and implied that interbreeding was common. But now I see that Monson and Phillips (1981) say that monsoni nests in the San Pedro valley and eastwards, with nelsoni in the rest of the state, and only one intermediate population identified! I’ll take a closer look at all of these and update the list soon.

  5. Thanks to all for the comments and suggestions. I’ve just updated the list adding some of Dan Lane’s additional subspecies (but not Wrentit, which seems to show a patchwork of local and clinal variations across California, mostly related to climate). I changed some English and Scientific names based on comments (Special thanks to Richard Klim at BirdForum for tracking down priority names for a bunch of subspecies). And I switched the English names so the subspecies names are in parentheses after the official species name, which seems to be a bit easier to follow (Thanks to Elias Elias for that suggestion). I still see a lot of inconsistent treatment in the list, but I’ll keep working on it and I’m confident that a lot of that can get sorted out over time.

  6. Hi David,

    In reference to:
    Sage Sparrow – Amphispiza belli

    Two subspecies groups differ consistently in plumage and song and are reliably identified in the field.
    Sage Sparrow (Pacific or Bell’s) – Amphispiza belli belli

    Sage Sparrow (Interior) – Amphispiza belli nevadensis group

    As I understand it, Sage Sparrow (nevadensis) is the monotypic form and that Bell’s Sparrow includes belli, clementae, cinerea and, based on recent work by Cicero, the “intermediate” canescens.

    Ref:
    Cicero (2010). The significance of subspecies: a case study of Sage Sparrows. Chapter 9 in Winkler & Haig. Avian Subspecies. Orn. Monographs 67

    Klicka & Banks (2011). A generic name for some sparrows. Zootaxa 2793:67-68.

    Best regards,

    David Donsker

  7. David,

    This is a really helpful resource and tracks well with the groups that we have been working on with eBird and Clements. I’ll continue to look this over in the coming days, but the seabird treatment to me immediately prompts a few comments, especially given the fact that NACC is out of sync with much of the world when it comes to seabird taxonomy (and I’m sure they’d appreciate receiving proposals…it’s not all their fault!).

    1) Yellow-nosed Albatross. The North American records hat are identifiable to subspecies are, not surprisingly, all ‘Atlantic’ Yellow-nosed Albatross (T. c. chlororhynchos), which have gray heads in adult plumage. This is quite different from the white-headed ‘Indian’ Yellow-nosed Albatross (T. c. bassi), and these taxa are split by many authorities.

    2) White-capped Albatross. The NACC has yet to split the Shy Albatross group and still uses the name Shy Albatross. SACC, Clements, and many others are using White-capped, Salvin’s, and Chatham Albatross. Regardless, to be consistent with NACC you should revise the English names to Shy (White-capped) and Shy (Salvin’s). The NACC is behind the times here, but surely is awaiting a proposal.

    3) Black-browed Albatross. While the “first” U.S. record from VA was an immature and tough to identify to subspecies, later photo records (photo of an adult off Newfoundland, and maybe another from Maine) show the expected dark-eyed form T. m. melanophris (or melanophrys, depending on whom you ask) rather than the ‘Campbell’ Black-browed Albatross (T. m. impavida). Again, many accord these forms species status.

    5) The NACC taxonomy for Little Shearwater is extremely outdated and the taxon recorded in North America–Puffinus [assimilis] baroli–was found by Austin et al. 2004 to group with Audubon’s and not with assimilis, which itself needs to be divided several ways. The question remains as to whether baroli would be monotypic (Barolo Shearwater), have two subspecies (including boydi) as Macaronesian Shearwater (as treated by the BOU), or be lumped within Audubon’s, which seems absurd. At the very least this situation deserves a comment like the one you have for Wandering Albatross.

    6) While on the topic of seabirds, it might be worth noting that North American records of Great-winged Petrel refer to gouldi; that Black-capped Petrel sensu NACC includes Jamaican Petrel, te extinct and utterly different dark bird; that North American forms of Audubon’s Shearwater are quite distinct from Galapagos Shearwater, Persian Shearwater, and Tropical Shearwater, which NACC still lumps under Audubon’s; that White-chinned Petrel sensu NACC includes Spectacled Petrel; and that Wilson’s Storm-Petrel may be due for some taxonomic revision, although this may or may not affect the birds that occur in the AOU area. Further, the NACC still lumps Brown Skua under Great Skua, and may be the only authority to do so.

    More to follow, but thanks again for providing this resource!

  8. In response to Marshal Iliff’s first seabird comment above(Yellow-nosed Albatross), I’d be keen to get feedback from Marshall, David, and anyone else with relevant experience on the records from Texas – for which a number of photos of specimens and live birds are displayed at the TBRC web site; they seem to show both gray-headed and white-headed birds, with some subtle differences in bill morphology…? Here’s a link to the page:
    http://texasbirds.org/tbrc/ynalbatr.htm
    Regards,
    Martin

  9. Hi Mr. Sibley. I would like to share with you some of my observations regarding Western Gull and Glaucous-Winged Gull:

    Among the subspecies of WEGU, the slightly paler northern birds also seem to average a bit larger. Grant mentioned this in his book as well. Another thing I’ve noticed is the 1st winter (1st basic) northern birds also seem to be a bit grayer, closely resembling the overall tone of same age Herring Gulls. Southern birds this age are browner compared to Herring Gulls as can be seen in this image: http://www.pbase.com/shonn/image/74510798.

    Among Glaucous-Winged Gulls I’ve made an observation after reading your description on the differences in long calls between Siberian and American (Washington in your example) birds. I noticed a while ago that some Glaucous-Winged Gulls have brighter pink legs than most. After having read you call descriptions, I’ve noticed the birds with the pinker legs almost always have the lower and slower calls you described (many of them are also a bit darker in mantel shade as well). None of this is conclusive of course but just some observations from a long time gull enthusiast. Here is a shot of a bird with the brighter pink legs: http://www.pbase.com/shonn/image/91159052 This particular bird did have a long call that was noticeably lower and slower than what I was used to hearing. Here’s a more typical bird with duller legs: http://www.pbase.com/shonn/image/110797210 It also had a more typical call although a bit slower than the birds I heard in Seattle but otherwise was the same.

  10. Hi David,

    Don’t know if this one has been mentioned or not, but I was wondering about subspecific variation in Black-whiskered Vireo(?). The nominate subspecies (Vireo altiloquus altiloquus) seems very distinctive in plumage coloration and bill size/shape to me compared to the coastal Florida form V. a. barbatulus. I believe the nominate subspecies occurs as a causal spring vagrant along the Gulf Coast with records from Louisiana and NW Florida panhandle (St. George Island). I’ve also had some birds here in Alabama in the spring that I highly suspected were probably the nominate form as well.

    Any thoughts?

    Cheers,
    Howard Horne
    Mobile, AL

  11. Hi David,

    A great resource, and thank you for putting all this information in one place. I really enjoy learning and looking for these variations in the field. Is there any chance that range maps will be added for these identifiable subspecies? Maybe in your next edition of your NA guide.

    Couple of minor comments, did you mean to include Labrador Duck? And have there been any records of Velvet Scoter in the US or Canada?

    Cheers

    Jim Hully
    Mundelein, IL

    1. Hi Jim, Thanks, I’m glad you find it useful. I do plan to continue adding information about subspecies, with maps, as I find the time. I did not mean to include Labrador Duck, but now that you’ve pointed it out I think I should add all of the extinct or presumed extinct species. There are no North American records of Velvet Scoter.

  12. Hi David,

    I also noticed that you only mention Masked Booby. Wasn’t there at least one record of the eastern Pacific race, S. d. granti, off California (e.g. I remember a juvenile in Monterey Bay in the late 90s), which would now be considered a full species, the Nazca Booby?

    Cheers,

    Jim Hully
    Mundelein, IL

    1. Nazca Booby is considered a full species but still no accepted records north of Mexico. I think there was a record in California suspected of being ship-assisted, and some records of immatures that may be Nazca but can’t be identified conclusively.

  13. Hi David,

    Do you know how I can find information on differentiating subspecies? I have seen a Black-crowned Night Heron in the Middle East (subspecies nycticorax) with what seems to be a thicker bill, but I couldn’t find any evidence of this difference with the North American subspecies. Can you help?

    Thank you.

    1. The best references for a starting point on subspecies are Pyle’s Identification Guide to North American Birds, The Handbook of Birds of the Western Palearctic, and the Handbook of Birds of the World. For most species you’ll want to dig deeper into the literature that is cited in those books. I checked Pyle for Black-crowned Night Heron and he lumps the North American and Eurasian birds in one subspecies because there are no reliable differences. In the Middle East you could get other subspecies from either India or Africa, which might be identifiable in the field, but I’m not familiar with the literature on those. [Actually, I just checked the Handbook of Birds of the World and I’m surprised to see that there is only one subspecies listed for all of Europe, Asia, and Africa! So if you see one that looks different it’s probably just a local variant and not a visitor from afar. Sounds to me like a good project for someone to look at DNA and study plumage in detail, because it seems really unlikely that they’re all the same.]

  14. Hi David,
    A while back I wrote to you about a population of Purple Finches that summers on our land in Nova Scotia. Instead of the customary raspberry colour, a large number of the males are yellow. I attached photos of a couple of the many individuals. I can’t find either my letter or a response on your sites. I now wonder if I was successful in posting it.

  15. Hi David,

    thanks for this list. Do you have a list of references for the various subspecies mentioned? I am particularly interested in references for hybridisation amongst subspecies (cline, interbreeding, intergradation, etc.) for the next updates of the Bird Hybrids Database.

    Regards,

    Serge Dumont
    MontrΓ©al, QuΓ©bec
    dumontse@gmail.com

  16. Dear David,

    A wonderful job. Can’t wait for the range maps.

    Erratum: American Coot, annotation – Caribbean
    Question: Wasn’t Xantus’s Murrelet recently split (Scripps’s, Guadalupe)?

  17. I feel that the Larids got short thrift in the above analysis. I could go into detail here if you’d like, but I think that improvements could be made to the entries for B-l Kittiwake, Mew, Herring, Yellow-legged, and LBB Gulls.

  18. David I clearly had nothing to do this afternoon…
    Here are some suggestions:-

    Are there no N. A. records of nominate marila Greater Scaup? If there are, then include in some way.

    Common Eider: your text refers to the β€œWest Arctic” form, but none of the 4 listed ssp. is called this – suggest using either β€œWest Arctic” or β€œPacific” in both places.

    Audubon’s Shearwater: according to Howell’s Tubenose book the lone Canadian specimen is attributed to loyermilleri, thus at least 2 subspecies occur in the ABA area. However this form is only distinguishable from Bahamian Audubon’s by measurements and thus probably not worthy of specific mention. However the Lesser Antillean form (true lherminieri if we call the Bahamian birds auduboni) is fairly distinct – at least as distinct as some of the recent splits in this group of Puffinus! – and this form likely (definitely? I have pics from Texas waters of a candidate) occurs in ABA waters.

    Wedge-rumped Storm-Petrel: nominate is the presumed form seen rarely off CA, but the lone U.S. specimen from inland CA is of ssp. kelsalli, which is a potential split per Howell’s Tubenose book.

    Lesser Frigatebird: the ME and MI records probably pertain to ssp. trinitatis while the CA and maybe the WY records pertain to ariel. I don’t know to what extent these forms differ.

    Masked Booby: see precedent set by Snowy Plover; the same format can be used to say that so far all N.A. records are of dactylatra.

    Great Blue Heron: mention β€œWurdemann’s – ?

    Turkey Vulture: there are at least two ssp. with described physical differences.

    Spotted Rail: perhaps say that there are two fairly distinguishable ssp possible: the Texas record appears to be the spot-backed insolitus of Mexico and Central America (based on photos of the specimen) while the ssp. of the PA record is unknown (is it?) but more likely to be the streak-backed maculatus from the Caribbean and South America.

    Ditto for Paint-billed Crake: TX specimen IDed as paler, white-throated nominate while VA specimen IDed as darker, gray-throated olivascens.

    Purple Swamphen: mention that some ssps and ssp-groups are considered separate species, and that birds in Florida are of the form ???? (precedent as with Lesser Sand-Plover and Snowy Plover).

    Common Moorhen now Common Gallinule

    Common Ringed Plover: 2 ssp widely recognized (nominate and tundrae)

    Whimbrel: mention that the β€œAmerican” form is split in Europe as Hudsonian Whimbrel; I recommend that you use β€œHudsonian” rather than β€œAmerican” else you will upset the Canadians!

    Numenius phaeopus phaeopus should be suffixed β€œ(group”) since it includes alboaxillaris.

    Semip. Sand: perhaps mention average differences in bill size geographically, as done with other species?

    Common House-Martin: NE Canada record likely nominate, while AK birds lagopudum (a specimen) that has more extensive white on the rump.

    Arctic Warbler North American ssp. listed as kennicotti in all my references, even as recently as 6th Ed of Nat Geo guide – ?

    Stonechat: follow example of Lesser Sand-Plover: eastern forms, including ssp. maurus often split as Siberian Stonechat. All North American records have been of ssp maurus.

    Gray-cheeked Thrush: mention alicae/minimus, and mention that sp. minimus clouds ID of Bicknell’s away from breeding and wintering grounds).

    Redwing: NE records likely coburni; WA record likely iliacus – don’t know if they are field-separable – ?

    Streak-backed Oriole: The 2 TX records could be from different ssp. than west coast records – ??

    Consider adding the ssp. name for all the polytypic (that are field-discernable in your view) vagrants. If the aim here is to help the viewer know which forms to prepare for in the field, then it would help to know that the Willow Warbler you might find in AK is not going to look exactly like the Willow Warbler in your European FG.

  19. I was wondering, what is Ward’s Heron? I have read old records, that it was in many ways like unto the Great Blue Heron, yet significantly larger, with yellowish legs.

  20. Lovely list. A couple of things, though.

    Had an influx of distinctly different darker-mantled, thinner-billed GW’s arrive after a Siberian cold front arrived in North Vancouver BC. One might have been a Herring X GW, but twenty identical adults arriving on the same day? That Aleutian Arc/Kamchatka Peninsula is clearly an area where larid genetics is pretty volatile.

    Kidding, right? I’ve seen a 1st cycle ‘barrovianus’ Glaucous barely bigger than an adjacent California Gull, and in South Delta BC a huge, presumably ‘pallidus’ Glaucous from Siberia which towered over the nearby GW’s the way a large male Great Black-Backed would dominate the local Herring Gulls. Yet both are called Glaucous Gulls.

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