BIRDS OF NORTH AND MIDDLE AMERICA 561 



tudinal, irregularly hexagonal, scales, these arranged in double 

 series on both acrotarsium and planta tarsi,*^ the anterior and pos- 

 terior series sometimes in close juxtaposition, sometimes separated 

 (at least on outer side) by a space (more or less wide) either covered 

 with small scales or without scales; middle toe, without claw, about 

 one-half as long as tarsus, the lateral toes decidedly shorter, either the 

 outer or the inner slightly exceeding the other in length, the hallux 

 much shorter than either of the lateral toes, and, together with inner 

 toe, very stout; claws relatively large, strongly curved, and acute, 

 that of the hallux largest and as long as or longer than its digit. 



Plumage and coloration. — Plumage soft and rather lax, especially 

 on underparts; edges of primaries (especially distal portion) soft and 

 semidecomposed (much as in Striges); longer auricular plumes and 

 feathers along posterior margin of auricular region very rigid, with 

 rounded, imbricated tips, forming a "facial ruff," as in Striges and 

 Buteonine genus Circus; whole orbital region, including the long super- 

 ciliary shield, naked; lores naked, but rather sparsely covered with 

 antrorse fine hairlike bristles, which also cover whole of cere posterior 

 to nostrils, those of upper portion of cere with tips strongly curved 

 backward; feathers of pileum rather long, forming, when erected, a 

 bushy crest. Adults with upperparts plain slate-gray, hair brown, 

 sepia, or rufous, the tail darker tipped and crossed by one to five bands 

 or bars of whitish; underparts whitish or bufFy, immaculate, more or 

 less barred with dusky, or with a few crescentic bars of pale grayish 

 on sides of breast and blackish shaft lines on flanks, et cetera. Young 

 more brownish above, the underparts white or buffy with or without 

 broad bars of dusky. Sexes essentially alike, but young distinctly 

 different in coloration from adults. 



Nidijication. — Eggs unknown; the nest said to be built in tall trees. 



Range. — Southern Mexico to Paragua}^, southern Brazil, etc. 

 (Four species.) 



KEY TO THE SPECIES AND SUBSPECIES OF MICRASTUR 



a. Size larger, wing more than 200 mm. in length. 



6, Wing under 230 mm. in length; upperparts dark slate gray, or dark brown, 

 c. Dorsal surface of tail crossed by three narrow white bands, each of which 

 encloses a mottled or uniform band of deep mouse gray (Costa Rica to 

 western Colombia), 

 d. With bro^Tiish or dark graj-ish brown upperparts. 



M. mirandoUei extimus, juv. (p. 573) 

 dd. With the upperparts dark slate-gray. 



M. mirandollei extimus, ad. (p. 572) 



" I am unable to find any difference in the scutellation of the tarsi between the larger and smaller species, 

 such as is alleged to exist by Swann (Synopt. List Accip., part 2, 1919, 15, 16). Even if such differences did 

 exist, and the two groups were generically separable, the name Ctimacocercus Cabanis is not available for the 

 smaller species, since its type is expressly stated by Cabanis to be Falco brachypterus Temminck (=SpaT- 

 viui melanoleucus Vieillot). 



