BIRDS OF NORTH AND MIDDLE AMERICA 275 



BUTEO ALBONOTATUS ALBONOTATUS Kaup 



NoRTHEKN Zone-tailed Hawk 



Adult (sexes alike) . — Form rather light and slender, but wings and 

 tail large, well developed; four outermost primaries with inner webs dis- 

 tinctly emarginated; middle toe not decidedly, if any, longer than the 

 bare portion of tarsus in front; plumage uniformly black or black with 

 a faint brownish cast, the feathers pure white basally; the upper back 

 and breast with a slight slate tinge m some specimens; lores and a 

 narrow frontal line whitish; loreal feathers with dark shafts; inner 

 webs of remiges paling to deep neutral gray and to grayish white, 

 barred with fuscous-black; the outer webs of all but the outermost 

 primary indistinctly barred with fuscous-black and deep neutral 

 gray; fourth primary longest; third scarcely shorter; fifth but little 

 shorter than thu'd; second intermediate between fifth and sixth; 

 first equal to eighth; both webs of the middle pair of rectrices and the 

 outer webs of the other tail feathers slate color, narrowly tipped with 

 white and very broadly subterminally banded with black and irregu- 

 larly banded with black on the basal three-fifths, the inner webs of 

 all but the median pair whitish; entire body, under wing coverts and 

 tail coverts black; iris dark brown to reddish brown; cere bright 

 yellow; bill black paling to light grayish white at base; tarsus and toes 

 bright yellow; claws black. 



Immature (sexes alike). — Generally similar to adults, but the 

 feathers of the underparts, especially the throat, breast, and upper 

 abdomen, the nape, upper back, and upper tail coverts, spotted with 

 white; feathers of the lower back and scapulars, and the upper wing 

 coverts narrowly edged with dark Vandyke-brown; remiges as in adult; 

 tail deep dark Vandyke-brown, faintly tipped with paler, and crossed 

 by numerous narrow oblique bands of black; subterminal one broad- 

 est, about 18 mm, wide; the next one is not a fourth as wide and 

 crosses about 25 mm, anterior to the last; the distance between the 

 black bands diminishes toward the base of the tail, so that after the 

 seventh of these no more can be distinguished; inner webs fading into 

 whitish internally, especially on the lateral feathers; bill black at tip; 

 bluish brown at base; iris dark brown. 



Juvenal (sexes alike). — Similar to immature, but with a little more 

 white spotting and with more of a brownish cast on the brown-edged 

 feathers of the upperparts. 



Natal doum. — Not known. 



Adult male.— Wing 380-393 (387.5); tail 216-222.8 (219.9); culmen 

 from cere 21.5-22.3 (21.9); tarsus 66.8-71 (69.5); middle toe without 

 claw 39.3-44.9 (42.2 mm.).=^^ 



^* Seven specimens from Texas, Arizona, and Mexico. 

 839094—50 19 



