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 Birdforum 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 *
Lesser Whitethroat – Sylvia curruca
Wrentit – Chamaea fasciata
Sedge Warbler – Acrocephalus schoenobaenus
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
38 thoughts on “Field Identifiable Subspecies of birds – an annotated list”
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.
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.
It looks like there’s a reference in Birds of North America online that calls the gnoma group the Mexican Pygmy-Owl. That’s a good precedent for that name.
Is this list available as a .pdf or in some other downloadable format?
Not now (it’s still a draft with some basic fact-checking and editing to be done), but I will try to make it available as a pdf once the reviews are finished.
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.
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.
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?!
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.
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.
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.
Hi, David –
This is a great resource! Thank you very much!
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.
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.
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.
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!
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:
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.
Also, Olsen and Larsson in “gulls of North American, Europe and Asia mention that Siberian GWGU also have a slightly darker mantel just as I mentioned.
I found a mistake in the list: the genus Peucaea. You wrote “Pucaea”.
Thanks, It’s fixed now.
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.
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?
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.
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?
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.
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?
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.]
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.
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.
The western form of Solitary Sa-dpiper (Sandpiper) is misspelled in the list.
Thanks Ken, It’s fixed.
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)?
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.
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 “West Arctic” form, but none of the 4 listed ssp. is called this – suggest using either “West Arctic” or “Pacific” 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 “Wurdemann’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 “American” form is split in Europe as Hudsonian Whimbrel; I recommend that you use “Hudsonian” rather than “American” else you will upset the Canadians!
Numenius phaeopus phaeopus should be suffixed “(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.
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.
Ward’s Heron is the southeastern subspecies of Great Blue Heron – wardi. In the field it is essentially indistinguishable from Great Blue Herons of other regions.
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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