464 BIRDS OF ILLINOIS. 



GENUS BUTEO CUVIER. 



Buteo Ctrv. Loc. Anat Comp. i, 1800, tabl. ois. Type, Falco buteo LINN. 



Craxirex GOULD, Voy. Beag. Birds, 1841,22. Type, Polyborus galapagoensis GOULD. 



Tachytriorchis KAUP, Class. Saug. Vog. 1844, 143. Type, Falco pterocles TEMM., 

 Buteo albicaudatus YIEILL. 



Poecilopternis KAUP. Isis, 1849, 329. Type, Falco pennsylvanicus WILS. 



Buteola BONAP. Compt. Bend, xli, 1855, 651. Type, Buteo bracfiyurus VIEILL. 



GEN. CHAE. Form robust and heavy, the wings long and rather pointed, the tail 

 moderate and rounded, the bill and feet strong. Bill intermediate between that of Astur 

 and that of Parabuteo. Wing long and rather pointed, the third to fifth quill longest, the 

 first shorter than eighth ; three or four with inner webs emarginated. Tail moderate, 

 slightly rounded. 



A. Four outer primaries with inner webs emarginated. 



a. Tarsus more than twice as long as the middle toe. 



1. B. lineatus. Tail always dusky, crossed by white or buff y narrow bands; outer 

 webs of primaries, anterior to their emarginations, more or less spotted with 

 white or ochraceous. Adult. Lower parts rufous (varying in intensity), more or 

 less barred or transversely spotted with white (breast sometimes nearly uniform 

 rufous). Tail and primaries slate-black, the former barred, the latter spotted on 

 outer webs with pure white ; lesser wing-coverts dark rufous or chestnut Young. 

 Lower parts dull whitish or buffy, longitudinally striped with dusky. Primaries 

 and tail brownish dusky, the former crossed by narrow bands of pale grayish 

 brown, buffy, or dull whitish, the latter spotted towards base with the same. Male. 

 Wing, 12.90-13.50; tail, 7.70-9.70; tarsus, 2.70-3.25. Female. Wing, 13.35-14.25; tail. 

 9.00-10.00; tarsus, 3.10-3.20. 



b. Tarsus less than twice as long as middle toe. Form decidedly more robust. 



2. B. borealis. Tail rufous in adult, brownish gray banded with black, in young; 

 outer webs of primaries without light spotting. Adult. Lower parts varying 

 from entirely white, with a few dusky markings on abdomen and flanks, to dusky, 

 with or without a rufous breast-patch. Tail rufous, usually with a single subter- 

 minal black bar, sometimes with indications of other bars, rarely without any 

 bar. Toung. Lower parts white, more or less varied with dusky, especially across 

 abdomen, or almost wholly dusky (in some western specimens). Tail brownish 

 gray, crossed by about 9 narrow bands of blackish. Male. Wing, 13.50-16.50; tail, 

 8.50-10.00; tarsus, 2.40-3.20. Female. Wiug,15. 25-17.75; tail, 9.50-10.50 ; tarsus, 3.15-3.40. 

 8. B. harlani. Similar in form to B. borealis, but lateral toes nearly equal, and 

 tibial plumes better developed, reaching to or beyond the base of the toes. Pre- 

 vailing color blackish, the bases of the feathers pure white. Adult. Tail con- 

 fusedly mottled with grayish, dusky and white, in variable relative amount, often 

 mixed with rufous, and crossed by a subterminal bar or narrow band of dusky. 

 Young. Tail crossed by 7-9 bands of grayish brown and dusky, the two colors 

 about equal in width. Male. Wing, 14.25-15.00; tail, 8.80-10.00; tarsus, 2.75-3.25. . 

 Female. Wing, 15.75-16.2C; tail, 9.10-10.00; tarsus, 2.90-3.50. 



B. Only three outer primarias with inner webs emarginated. 



5. B. swainsoni. Size lar?e (wing more than 12 inches), the tips of the closed wings 

 reaching nearly or quite to the end ot the tail. Tail (of both adults and young) 

 grayish brown (sometimes with a hoary cast), crossed by 9 or more narrow 

 dusky bands, these less distinct basally. Upper parts nearly uniform dusky brown. 

 Normal plumage. Lower parts whitish (or light colored), with a distinctly defined 

 breast-patch, rufous in the male, brown in the female. Melanistic plumage. 

 Lower parts entirely dusky, or with dusky prevailing, with or without admix- 

 ture of rufous. Young. Above brownish black, with ochraceous edgings to feath- 

 ers; beneath fine ochraceous, more or less marked with tear-shaped spots of 



