1/4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I50 



2]. Tibia russet to cinnamon, without bars; under surface without bars or 



streaks, buffy white to cinnamon-buff (immatures), or dark gray (adults). 



Bicolored hawk, Accipiter bicolor bicolor, p. 190 



Tibia not plain russet or chestnut without bars, under surface streaked or 



barred, or if plain, black to slate-black 28 



28. Loral area heavily feathered 29 



Loral area bare except for scattered bristles 31 



29. Smaller, wing 160 to 210 mm.; form slender, head small; tarsus and toes 



long and slender Sharp-shinned hawk, Accipiter striatus velox, p. 194 



Larger, wing more than 240 mm. ; form robust, head large ; tarsus and toes 

 larger, heavier 30 



30. Upper surface black, or brownish black, without definite streaks on the 



crown; under surface black, or white, usually plain, but in some with a 

 few narrow dusky streaks on the sides. 



Short-tailed hawk, Buteo hrachyurus, p. 202 

 Brownish gray, or grayish brown above, more or less mottled with cinna- 

 mon and white, especially on the crown ; below barred with white and dull 

 brown, or white more or less streaked with dusky. 



Broad-winged hawk, Buteo platyptertis platypterus, p. 204 



31. Much larger, wing more than 325 mm., tarsus more than 80 mm. 



Lesser black hawk, Buteogallus anthracinus, p. 232 

 Decidedly smaller, wing less than 260 mm. ; tarsus less than 75 mm 32 



32. Ground color clear gray, barred with white on lower surface, and mottled 



and barred above with dusky gray. 



Gray hawk, Buteo nitidus blakei, adult, p. 199 

 Ground color not clear gray 33 



33. Back and wings sooty black, with crown buffy white streaked narrowly with 



black; tibia plain buff. .Gray hawk, Buteo nitidus blakei, immature, p. 199 

 Back and wings not sooty black, tibia not plain buff 34 



34. Head, back, and wings grayish brown, lined and mottled with white and 



buff ; lower surface white, streaked with sooty brown ; tibia barred nar- 

 rowly with dusky. 



Gray hawk, Buteo nitidus blakei, immature, second stage, p. 199 

 Head, back, and wings plain grayish brown; breast, abdomen, and tibia 

 cinnamon, barred with white ; foreneck and upper breast dark gray. 



Large-billed hawk, Buteo magnirostris, p. 211 



35. Tail not more than half as long as wing. 



White-tailed hawk, Buteo albicaudatus hypospodius, p. 195 

 Tail more than half as long as wing 36 



36. Three outer primaries distinctly emarginate, or notched, on inner web. 



Swainson's hawk, Buteo szvainsoni, p. 208 

 Four outer primaries distinctly emarginate or notched on inner web. ... 37 



37. Black above and below, including under wing coverts; the under surface in 



immature birds lightly spotted with white. 



Zone-tailed hawk, Buteo albonotatiis, p. 197 



Upper surface of tail cinnamon-brown, with a black subterminal band 



(adult) ; or grayish, or blackish-brown, barred narrowly with dusky 



black (immature) Red-tailed hawk, Buteo jamaicensis, p. 206 



