BIRDS OF NORTH AND MIDDLE AMERICA 597 



very spacious interannular membrane, to which the intrinsic muscles 

 are attached, the last few tracheal rings being fused mesially in front 

 and behind. 



Plumage and coloration. — Lores, orbital, suborbital, and malar re- 

 gions and chin naked, with rather sparse fine bristles; entire cere 

 behind and below nostrils scantily covered with fine hairs; pileum 

 with well-developed normal feathers, these becoming considerably 

 elongated on occiput, where forming a rather distinct, depressed crest; 

 feathers of nape and hindneck well developed but softer and broader.^* 

 Tail dull white to pale Isabella color, narrowly barred with grayish 

 or dusky and crossed by a broad terminal band of dark brown or 

 black; adults with pileum and greater portion of body and wings dark 

 brown or blackish, the cheeks, neck, chest, and tail coverts dull white 

 to isabella color, the hindneck, breast, and back (sometimes wing 

 coverts and abdomen also) barred with dull white or isabella color 

 and dusky; young with pileum plain dull brownish, the rest of plumage 

 (except tail, et cetera) striped with dull brownish and dull whitish 

 or buffy. 



Nidification. — Nest in trees; eggs (usually 2-3) rounded ovate, 

 heavily spotted with reddish brown (sometimes uniformly this color, 

 rarely showing a whitish ground color) . 



Range. — Southern border of United States (Florida to Arizona) and 

 southward to southern extremity of South America; Guadalupe and 

 Tres Marias islands, northwestern Mexico, but not in West Indies. 

 (Three species, with additional subspecies.) 



KEY TO THE SPECIES AND SUBSPECIES OF POLYBORUS 



a. Breast barred or, at least, transversely spotted with dark brown or black, 

 h. The abdomen, thighs, and flanks barred with dark brown like the breast 



(Guadalupe Island; extinct) P. lutosus, ad. (p. 610) 



bh. The abdomen, thighs, and flanks unbarred, black or fuscous, or only the 

 upper abdomen barred, the rest blackish. 

 c. Scapulars and median upper wing coverts solid brownish or blackish, the 

 upper tail coverts unbarred white. 

 d. Back and wings black to very dark fuscous-black (Pearl Islands and 

 Dari^n south to Brazil and Peru). 



P. cheriway cheriway, ad. (p. 607) 

 dd. Back and wings not black but brown to very dark fuscous, 

 e. Back and wings paler, sepia (Tres Marias Islands). 



P. cheriway pallidus, ad. (p. 609) 

 ee. Back and wings darker, fuscous to dark fuscous (Florida, Gulf States, 

 West Indies, Mexico to Panama Canal Zone). 



P. cheriway audubonii, ad. (p. 600) 



'• The pterylosis of Polyborus is said (by Nitzsch, Pterylographia, p. 63) to be 

 peculiar "in having the dorsal portion of the spinal tract elliptically dilated upon 

 the caudal pit, where it incloses a narrow lanceolate insular space — a structure 

 which I have never met with elsewhere among the Falcons [Falcones]." 



