460 Field Museum of Natural History — Zoology, Vol. IX. 



1907, p. 93). While it may possibly breed in northern Wisconsin, 

 there is no record of its having done so. Messrs. Kumlien and 

 Hollister and Mr. Clark give it as a regular but by no means a com- 

 mon winter resident in Wisconsin. 



157a. Astur atricapillus striatulus Ridgw. 

 W^ESTERN Goshawk. 



Distr.: Western North America, from Idaho and Nebraska to 

 California and Alaska; accidental as far east as Mississippi Valley. 



Special cliaracters : The Western Goshawk may be distinguished 

 from the eastern bird by its sooty back and generally darker upper 

 plumage. In the immature bird, the black stripes on the under parts 

 are decidedly broader than in .4. atricapillus and the thighs are marked 

 with large black spots. 



Mr. Chas. K. Worthen writes me he has taken this bird near War- 

 saw. Its occurrence in Illinois must be considered as accidental. 



Genus BUTEO Cuvier. 



158. Buteo borealis (Gmel.). 

 Red-tailed Hawk. 



Distr.: Eastern North America and Canada, south to Mexico; 

 breeds nearly throughout its range. 



Adult male and female : Size, large; four outer primaries, notched; 

 upper surface of tail, rich rufous brown, with or without one or more 

 black bars, and tipped with white; some specimens have the tail 

 without bars, others with several (the latter seem more commonly to 

 be females) ; upper plumage, dark brown, mixed with whitish and 

 pale rufous brown; under parts, white; the feathers marked with pale 

 rufous brown on sides of neck, breast, and body; upper surface of 

 primaries, brown, faintly barred with dusky and becoming white on 

 the basal portion of the inner webs. 



Immature : General markings similar to adult, but differs in color; 

 the rufous brown replaced by cinnamon brown on the sides of throat, 

 breast, and body, and the under parts with more or less brown mark- 

 ings on the belly; the breast, usually plain white; tail quite different 

 from the adult, grayish brown, mixed with tawny and banded with 

 dark brown, the feathers tipped with white, and usually with more 

 or less white on the inner webs of the outer feathers, varying accord- 

 ing to age. 



