536 BULLETIN 50, UNITED STATES NATIONAL MUSEUM. 



twice as long as bill. Wing rather long, the distance from tip of 

 longest primary coverts to tip of longest primaries more than haK the 

 length of wing; eighth primary longest, the ninth and seventh, suc- 

 cessively, slightly (but decidedly) shorter, the tenth much shorter 

 than seventh; sixth to ninth primaries, inclusive, with outer webs 

 distinctly sinuated. Tail more than six-sevenths as long as wmg, 

 much rounded, the outer rectrices about four-fifths as long as middle 

 pair, the rectrices relatively rather narrow, not widening terminally. 

 Tarsus decidedly longer than middle toe without claw (but shorter 

 than middle toe with claw), more than one-seventh as long as wing, 

 naked, only the extreme upper portion in front being feathered; outer 

 toe without claw reaching to about middle of second phalanx of middle 

 toe, very slightly shorter than inner toe; hallux, with claw, about as 

 long as basal phalanx of middle toe. 



Plumage and coloration. — Plumage of pUeum blended, without spe- 

 cially developed feathers on sides of occiput; feathers of chest normal 

 (not forming a distinct flap or apron). Primaries unspotted (except, 

 in some females, on basal portion), but with a broad white band 

 crossing the four or five outer quills; inner webs of tliree outer rec- 

 trices (on each side) mostly white in males, the terminal portion of 

 inner web of third and fourth rectrices white in females. 



Range. — Mexico (and extreme southern Texas) to southern Brazil, 

 etc. (Monotypic, but the single species comprising five or six more 

 or less strongly characterir^ed geographic subspecies.) 



KEY TO THE SPECIES AND SUBSPECIES OP NYCTIDROMUS.a 



a. Smaller (wing averaging less than 162 in males, less than 160 in females). 



h. Darker and smaller; wing averaging 155.2 in male, 153.1 in female; tail averaging 

 144 in male, 136.3 in female. (Amazon Valley to Guianas and Panama and 

 northward to Chiapas and British Hondm'as.) 



Nyctidromus albicollis albicollis (p. 537). 



hh. Paler and larger; wing averaging 161.3 in male, 159.4 in female; tail averaging 



153.1 in male, 144.8 in female. (Pacific slope of Mexico, from Oaxaca to 



Sinaloa) Nyctidromus albicollis nelsoni (p. 544). 



aa. Larger (wing averaging more than 167 in males, more than 162 in females). 

 6. Wing averaging less than 172 in male, less than 163 in females; tail averaging less 

 than 164 in males, less than 145 in females. 



a This "key" is restricted to the forms occurring from Panama northward, the 

 available South American material being too scant to permit of satisfactory treatment, 

 except in the case of the extreme southern form, N. a. derbyanus. This occurs from 

 Bahia to extreme southern Brazil, southern Bolivia, etc., and is a very strongly char- 

 acterized form, nearly as large as the larger Mexican subspecies, but very different in 

 coloration. [Nyctidromus derbyanus Gould, Icones Avium, ii, 1838, pi. 12 (South Am.; 

 coll. Derby Mus). — N[yctidromus] albicollis derbyanus Hartert, Kat. Vogelsamml. 

 Mus. Senckenb., 1891, 120; Tierreich, Podarg., Caprim., Macropt., 1897, 32.— Nycti- 

 dromus albicollis derbyanus Allen, Bull. Am. Mus. N. H., v, 1893, 124 (Chapada, 

 Mattogrosso, s. w. Brazil; crit.); Hellmayr, Novit. Zool., xv, 1908, 79 (Goyaz, Rio 

 Thesouras, and Rio Aragua, s. Brazil; crit.).] 



