The western red-tailed hawk (Buteo jamaicensis calurus) is a subspecies of the red-tailed hawk. Description In wing chord males range from , averaging , and females range from , averaging . males and females average in tail length, in tarsal length and in culmen length. The two largest samples of body mass in B. j. calurus showed that in Idaho, around the greater area of the Snake River NCA, 90 males averaged and 113 females averaged , while 152 migrating B. j. calurus at the Goshute Mountains of Nevada averaged . Adult B. j. calurus are usually rangier and darker than the eastern red-tailed hawk (B. j. borealis), with pale individuals usually having a richer tawny base color (with occasionally a pale rufous color showing around the chest or neck), typically a heavily streaked breast and belly band, a brownish throat, dark barring on the flanks, a well-defined tawny V on the back and, occasionally, a tail with multiple bars. Dark morph B. j. calurus adults are typically all chocolate brown above and below (although sometimes variously even jet black or with a bit of tawny feather edging below) with a rufous tail, which sometimes has heavy blackish crossbars but is usually similar to other red tails. Intermediate or rufous morphs are rich rufous on the breast, with a broad, solid chocolate-brown belly band and heavily barred thighs and crissum. Like dark morphs, rufous morph adults usually lack the incomplete V on the back, but sometimes rufous feathers can manifest on one. Adults may show nearly endless variation in coloring and many may combine several characteristics of the three main morphs. Dark morph juveniles are usually mostly dark brown but with extensive pale mottling on the back and occasional tawny-edge feathers on the underside and slightly broader bars on the tail than pale morph B. j. calurus. Rufous morph immatures are more similar to pale morph ones but are considerably more heavily streaked almost everywhere below from the thighs to the upper chest. Individuals of northwestern Mexico may average paler than most B. j. calurus, lacking the typical dark wing markings. Distribution This race seems to have the greatest longitudinal breeding distribution of any race of red-tailed hawk, and put together with B. j. borealis these two subspecies may occupy nearly 75% of the breeding range of red-tailed hawks in North America. B. j. calurus reaches its northern limits as