FALCONID^ — THE FALCONS. 273 



the wing-formula cannot be ascertained. Wing, 15.50; tail, 8.50; tarsus, 2.50; middle 

 toe, 1.60. Length, 19^ ; extent, 47i. 



Young male (52,763, Mazatlan, Mex. ; Colonel A. J. Grayson). Generally similar to 

 the preceding; feathers of neck, back, and under parts more conspicuously spotted with 

 white beneath the surface, these spots considerably exposed on the breast and upper tail- 

 coverts. Tail deep dark vandyke-brown, faintly tipped with paler, and crossed with 

 numerous narrow oblique bands of black ; subterminal one broadest, being about three 

 fourths of an inch in width ; the next one is not a fourth as wide, and crosses about an 

 inch anterior to the last ; the distance between the black bands diminishes towards the 

 base of the tail, so that after the seventh of tliese, no more can be distinguished. Inner 

 webs passing into whitish towards edges, this prevailing on lateral feathers. Fourth quill 

 longest; third scarcely shorter; fifth but little shorter than tliird; second intermediate 

 between fifth and sixth ; first equal to eighth. Wing, 15.30 ; tail, 8.80 ; tarsus, 2.40 ; 

 middle toe, 1.00. Length, 15f ; alar extent, 48. Bill black at tip, bluish-brown at base ; 

 iris dark brown. 



Hab. Guatemala, Mexico, and adjoining parts of United States; Arizona (Coues); 

 Santa Clara Co., Cal. (Cooper). 



LIST of specimens EXAMINED. 



National Museum, 2 ; Philadelphia Academy, 2. Total, 4. ' 



There can be but little doubt that this plumage denotes a younger stage 

 of the same species as the B. zonocercus of Sclater. The adult bird described 

 above is moulting, and two tail-feathers of the old plumage, wliich have 

 not yet been cast, are precisely like those of this specimen, the new ones being 

 entirely different, as will be seen by the description. Taking with this the 

 exact similarity of the pattern of under side of primaries, as well as the 

 plumage in general, and the sameness of proportions, one cannot but be con- 

 vinced of their identity. The localities of the two specimens are also so 

 near that it is scarcely possible they are distinct. 



The plumage of this stage is parallel, in its relation to the adult, with 

 that of the young of B. alhifrons var. minutus, both differing from the mature 

 stage in nearly the same particulars, the more numerous bands on the tail 

 distinguishing the young of nearly all Buteos from adults of the same 

 specis. 



An adult specimen from Mexico, in the collection of the Philadelphia 

 Academy (without number or other indications on the label), though resem- 

 bling the two specimens described, in all essential points, differs from them 

 in regard to the coloration of the tail. The main differences are as follows : 

 Tail deep black basally and subterminally, the tip (very narrowly) and a 

 middle zone about 2.00 inches broad, and 1.80 from the tip, being duller 

 and more brownish-black, this irregularly defined anteriorly, but of sharp 

 regular definition along the posterior border; the subterminal black band 

 is very precisely defined on the inner webs, and anterior to this nearly the 

 whole inner web is white, irregularly blotched witli black towards the base, 

 however ; the markings of somewhat longitudinal direction ; the outer webs 

 are black to the very base. Wing, 16.50 ; tail, 9.00 ; tarsus, 2.70; middle 

 toe, 1.80. Wing-formula, 4, 3 - 5 -2 - 6 - 7, 1. 



vor,. III. 3.5 



