Western Spindalis  Spindalis zena
     Green-backed S. z. ??
     Black-backed

Summer Tanager Piranga rubra
     Eastern  P. r. rubra
     Western  P. r. cooperi group

Northern Cardinal Cardinalis cardinalis
     Southwestern  C. c. superbus
     Eastern  C. c. cardinalis group

Painted Bunting Passerina ciris
     Eastern  P. c. 
     Western  P. c. 

Eastern Towhee Pipilo erythrophthalmus
     Red-eyed  P. e. erythrophthalmus group
     White-eyed  P. e. alleni

Spotted Towhee  Pipilo maculatus
     Pacific Northwest  P. m. oregonus group 
     Southwest  P. m. montanus group
     Great Plains  P. m. arcticus

Bachman's Sparrow Aimophila aestivalis
     Western  A. a. illinoensis
     Eastern  A. a. aestivalis

Botteri's Sparrow Aimophila botterii
     Texas  A. b. texana
     Arizona  A. b. arizonae

Rufous-crowned Sparrow Aimophila ruficeps
     Pacific  A. r. ruficeps group
     Interior  A. r. scottii group

American Tree Sparrow  Spizella arborea
     Pale  S. a. ochracea
     Dark  S. a. arborea

Brewer's Sparrow Spizella breweri
     Southern   S. b. breweri
     Northern (Timberline)  S. b. taverneri

Field Sparrow  Spizella pusilla
     Gray  S. p. arenacea
     Rufous  S. p. pusilla

Black-throated Sparrow Amphispiza bilineata
     Texas  A. b. bilineata
     Intermediate  A. b. opuntia
     Western  A. b. deserticola

Sage Sparrow Amphispiza belli
     Interior  A. b. nevadensis
     Pacific (Bell's)  A. b. belli
These two subspecies are easily distinguished by plumage and song, and species status has been proposed. The situation is complicated somewhat by an intermediate subspecies, A. b. canescens, in interior California.

Savannah Sparrow Passerculus sandwichensis
     Typical P. s. sandwichensis group
     Ipswich P. s. princeps
     Belding's P. s. beldingi
     Aleutian P. s. sandwichensis group
     Large-billed Sparrow P. s. rostratus group
Variation in this species is considerable with a number of named subspecies across North America. Most variation is clinal, however, and only a few subspecies and subspecies groups are really distinguishable. In general subspecies in the east and in humid Pacific coastal areas are more rufous, while those in the drier interior are gray, but there is considerable variation and I found it difficult to separate broad eastern and western groups among the continental birds. Of these the most distinctive in plumage, structure, voice and DNA is the Large-billed group, which has been proposed for species status. In the past Ipswich has been considered a separate species, a treatment supported by its isolation during the breeding season and clearly different size and plumage.

Grasshopper Sparrow Ammodramus savannarum
     Northern  A. s. pratensis group
     Florida  A. s. floridanus
Within the Northern pratensis group there are several subspecies, the most distinctive of which is the relatively pale and rufous Arizona population A. s. ammolegus.
 
 Nelson’s Sharp-tailed Sparrow
     Interior  A. n. nelsoni/alterus
     Atlantic  A. n. subvirgatus

Seaside Sparrow Ammodramus maritimus
     Atlantic  A. m. maritimus group
     Gulf Coast  A. m. sennetti group
     Cape Sable  A. m. mirabilis 
     [Dusky]  A. m. nigrescens

Fox Sparrow Passerella iliaca
     Red (Taiga)  P. i. iliaca group
     Sooty (Pacific)  P. i. unalaschensis group
     Slate-colored (Interior West)  P. i. schistacea group
     Thick-billed (California)  P. i. megarhyncha group

Song Sparrow Melospiza melodia
     Eastern M. m. melodia  
     Pacific Northwest  M. m. morphna
     Aleutian  M. m. maxima
     Central California coast  M. m. gouldii
     Southwestern  M. m. saltonis
There are 29 named subspecies of Song Sparrow listed in Pyle, and I have tried to show the range of variation by illustrating these five subspecies, but all variation is clinal and it is difficult to categorize the other 24 subspecies into groups.

White-crowned Sparrow Zonotrichia leucophrys
     Eastern Taiga  Z. l. leucophrys
     Western Taiga  Z. l. gambellii
     Interior West  Z. l. oriantha
     Pacific  Z. l. nuttalli group (includes Z. l. pugetensis)
 
Dark-eyed Junco Junco hyemalis
     Slate-colored  J. h. hyemalis group
     Canadian Rocky Mountains  J. h. cismontanus
     Oregon  J. h. montanus group
     Pink-sided  J. h. mearnsi
     Gray-headed  J. h. caniceps
     Red-backed  J. h. dorsalis
     White-winged  J. h. aikeni

Red-winged Blackbird Agelaius phoeniceus
     Typical  A. p. phoeniceus group
     Bicolored  A. p. californicus group
This is another complex species, with 14 named subspecies. Variation is somewhat clinal and there are several named subspecies intermediate between these two. Identification may be difficult or impossible in practice. 

Eastern Meadowlark Sturnella magna
     Typical  S. m. 
     Lilian’s (Southwestern) S. m. lilianae

Great-tailed Grackle Quiscalus mexicanus
     Eastern  Q. m. prosopidicola
     Western  Q. m. nelsoni

Boat-tailed Grackle Quiscalus major
     Atlantic  Q. m. torreyi
     Gulf Coast/ Florida  Q. m. major group 

Common Grackle Quiscalus quiscula
     Interior (Bronzed)  Q. q. versicolor
     Coastal (Purple)  Q. q. stonei
     Florida  Q. q. quiscula

Bronzed Cowbird Molothrus aeneus
     Eastern  M. a. aeneus
     Western  M. a. loyei

Brown-headed Cowbird Molothrus ater
     Eastern  M. a. ater
     Pacific/Mexican  M. a. obscurus
The intermediate population is named M. a. artemisiae. 

Hooded Oriole Icterus cucullatus
     Western  I. c. nelsoni
     Eastern  I. c. sennetti
The intermediate population is named I. c. cucculatus.

Gray-crowned Rosy Finch Leucosticte arctoa
     Interior (Gray-crowned)  L. a. tephrocotis group
     Coastal (Gray-cheeked or Hepburn's)  L. a. littoralis group
     Bering Sea  L. a. griseonucha group

Pine Grosbeak Pinicola enucleator
     Pacific  P. e. flammula group
     Interior West  P. e. montanus group
     Taiga  P. e. leucurus

Purple Finch Carpodacus purpureus
     Eastern  C. p. purpureus
     Pacific  C. p. californicus

Red Crossbill Loxia curvirostra
The current state of crossbill taxonomy in the northern hemisphere defies subspecies names. Nine different call types corresponding to subtle differences in bill size have been diagnosed in North America (and recent research in Europe has uncovered a similar situation there). These populations have been designated by numbers or letters - e.g. types 1-9 or a-i - and for the most part do not correspond to previously named subspecies. Under the circumstances I think it is simplest to ignore all previous subspecies names and refer to these birds simply by the number or letter designations, rather than trying to reconcile the two systems of naming. More information can be found in the technical literature.

Common Redpoll Carduelis flammea
     Southern  C. f. flammea
     Greenland (Greater)  C. f. rostrata

Hoary Redpoll Carduelis hornemanni
     Southern  C. h. exilipes
     Greenland  C. h. hornemanni

Lesser Goldfinch Carduelis psaltria
     Western  C. p. psaltria
     Texas  C. p. mexicanus

Evening Grosbeak Coccothraustes vespertinus
     Eastern  C. v. vespertinus
     Western   C. v. montanus group