FALCONID.E — THE FALCONS. 257 



B. Four outer primaries with their inner webs cut. 



a. Form hght, the legs slender; tail of adult without a subterminal band 

 of black more distinct than the others. 



3. B. zonocercus. Wing, 15.50-17.40; tail, 8.50-10.75; culmen, 

 .90; tarsuy, 2..J0-2.80; middle toe, 1.60-1.85. Entirely deep black, 

 with more or less concealed pure white spotting. Adult. Tail car- 

 bonaceous-black, with three very broad zones, of pure white on inner 

 webs and ash on the outer webs. Young. Tail dark lirown, the inner 

 webs more or less, sometimes entirely, white, crossed by numerous 

 oblique bands of black. Hah. Mexico (chiefly western?) and adjacent 

 southwestern portions of the United States (Arizona, Coues ; Southern 

 California, San Diego, Cooper). 



4. B. lineatus. Wing, 11.25-14.25; tail, 8.00-10.00; culmen, .75- 

 .90; tarsus, 2.70-3.25; middle toe, 1.30-1.50. Fourth to fifth quill 

 longest ; first shorter than seventh. Outer wel3s of the primaries with 

 quadrate spots of whitish; lesser wing-coverts dark rufous; lower 

 parts rufous more or less barred with whitish, or whitish spotted longi- 

 tudinally with dusky. Adult. Head, neck, lesser wing-coverts, and 

 lower parts deep rufous, the lower parts more or less barred posteriorly 

 with whitish. Primaries and tail black; the former with quadrate spots 

 of pure white on the outer webs, and the latter crossed by six narrow 

 bands of pure white, and tipped with the same. Young. Head, neck, 

 and lower parts whitish, usually more or less tinged with ochraceous, 

 and with longitudinal markings of dusk3\ Primaries and tail dusky; 

 the former mostly ochraceous anterior to the sinuation of their outer 

 webs, the latter crossed by numerous narrow bands of pale grayish- 

 brown, these becoming paler and more ochraceous toward the base. 

 Lesser wing-coverts more or less tinged with dark rufous. 



Adult. Lower parts light rufous barred with Avhite. Young. 

 White prevailing on the lower parts. Hah. Eastern Province of 



the United States var. lineatus. 



Adult. Lower parts deep dark rufous, almost free from bars, except 

 posteriorly. Young. Dark spotting on the lower parts pre- 

 dominating. Hah. Pacific Province, and southern Western Prov- 

 ince, of the United States var. elega ns. 



h. Form robust and heavy, the tarsus stout; tail of the adult with a sub- 

 terminal band of black broader than the other. 



5. B. borealis. • Wing, 13.25-17.75; tail, 8.50-11.30; culmen, .90- 

 1.15 ; tarsus, 2.70 - 3.40 ; middle toe, 1.60 - 1.95. Weight, 2^ to 4 lbs. 

 Third to fifth quill longest ; first shorter than seventh and shorter than 

 tenth. Colors extremely variable, ranging from entirely pure white 

 beneath, through various shades of ochraceous and rusty, and greater 

 or less amount of darker spots and bars, to'an entirely uniform brownish- 

 black. Adult. Tail deep rufous, generally paler at the tip; with or 

 without black bars. Young. Tail grayish-brown, crossed by nine or 

 ten bands of black, much narrower than the gray ones. Lower parts 

 always with Avhite predominating. 



Tibiae and lower tail-coverts without transverse bars, at any age. 

 Lower parts with white always predominating. Tail never with 

 more than one bar of black. 



Feathers of the head and neck edged laterally with rufous ; 

 scapulars and wing-coverts much variegated with whitish ; 

 VOL. irt. 33 



