NYCTIDROMUS.—CHORDEILES., 395 
size. The bird from the Lower Rio Grande Valley has been recently separated by 
Mr. Sennett as Myctidromus albicollis merrilli?’, and this course was endorsed by 
Mr. Hartert *8. But on re-examining the large series of specimens in the British 
Museum we do not think such a distinction can be maintained. Rio Grande birds are, 
perhaps, rather greyer on the upper plumage, especially on the head, and they are 
rather large; but they can be matched almost exactly by birds from many other places. 
Moreover, the range of this species is no doubt quite continuous, and the Rio Grande 
birds only represent it at its extreme northern boundary. 
Nyctidromus albicollis is by far the commonest species of Goatsucker in Mexico and 
Central America. Its distribution is nearly universal in the low-lying districts up to 
an elevation of about 5000 feet in the mountains. It affects the more open thinly 
wooded districts rather than the dense forests, though it occurs in open glades. 
After nightfall its presence is made known to the traveller by its habit of flitting in 
front of the horseman and settling from time to time in the middle of the track. Its 
familiar note, which resembles the words ‘“ Who are you?” may be heard throughout 
the night. 
This bird makes no nest, but lays its two eggs on the bare ground. ‘These are of a 
pinkish-buff colour with darker spots. Salvin found an egg on bare ground about the 
middle of May near Obispo Station on the Panama Railway, close to the edge of the 
forest; and Mr. Merrill also took a nest near Hidalgo in Southern Texas on 15th 
May; but Mr. Sennett met with one in the same district as early as 20th April. 
b. Rictus glaber, setis elongatis nullis. 
CHORDEILES. 
Chordeiles, Swainson, Fauna Bor.-Am. ii. p. 496 (1831); Hartert, Cat. Birds Brit. Mus. xvi. 
p. 609. 
Chordeiles is the only Central-American genus of Caprimulgide which is destitute of 
the strong, long, rictal bristles so characteristic of the foregoing genera. Three other 
genera, Nyctiprogne, Podager, and Lurocalis, all of them belonging to South America, 
have the same character; and two Old World forms, Lyncornis and Eurystopodus, are 
also destitute of rictal bristles. Amongst other characters distinguishing Chordeiles 
from Central-American forms is the forked tail. 
Of the four definite species recognized by Mr. Hartert, divisible into nine imperfectly 
segregated forms, two only occur within our limits. One of these is the well-known 
C. virginianus and its modification C. henryi, and the other, C. texensis, a northern 
form of the South-American C. acutipennis. Both, after the usual habit of their kind, 
are probably more or less migratory. 
50* 
