41 6 CORACIIFORMES 



CHAP. 



noptilus nuttalli. The characteristically soft plumage shews an 

 intricate mixture of brown, grey, fawn, black, and white, and is 

 ordinarily barred and minutely freckled, but frequently patched or 

 spotted with white ; it is, however, impossible in a limited space to 

 describe the species in detail, though it may be noticed that several 

 have reddish nuchal collars ; and some exhibit rufous and grey phases 

 unless, as may be the case, the rufous forms are females while 

 others from arid districts have a protective coloration of a more 

 or less sandy hue. In the Podargidae large powder-down patches 

 occur laterally on the rump, in the Nyctibiinae on the breast and 

 sides. The sexes are often alike, the young either resembling the 

 female, or assuming the full plumage at once. Lyncornis, Otophanes, 

 and Batrachostomus have head-tufts like those of some Owls, the 

 constituent feathers in the last genus being bristle-pointed. 



Nightjars are found in most parts of the world, while the 

 northern species habitually move southwards for the winter, 

 Podager and Chordiles, at least, Hocking in August and 

 September. The most typical forms are distinctly crepuscular, 

 and pass the day as our British bird does quiescent on the 

 soil, or upon some post or fence, often concealing themselves 

 below shrubs or herbage, or in hollow stumps. At such times 

 they will almost permit themselves to be trodden upon before rising 

 from the ground, and sit with their eyes closed ; on branches 

 the body is ordinarily placed lengthwise, but on thin palings 

 or wire this is of course impossible. Nyctidromus exhibits more 

 terrestrial habits, and walks instead of shuffling ; the American 

 "Bull -bat" {Chordiles virginiamts) hawks in the full glare of 

 the sun. The more diurnal species frequently rise to a consider- 

 able height in the air, sailing backwards and forwards with an 

 easy, flapping motion, descending with undulating swoops, or 

 remaining momentarily poised aloft, and then darting suddenly 

 upon their prey ; the flight of their nocturnal allies is w"eaker 

 and more lowly, being jerky, twisting, and erratic. Some forms, 

 if not all, when inspecting an intruder turn the head almost 

 completely round. The vibrating sound often accompanying 

 the passage through the air may be produced by the wings 

 coming into contact, as is the clapping noise occasionally heard ; 

 but the cause is not certainly ascertained, nor is that of the far- 

 resounding " churr " uttered by the male of the Common Nightjar 

 while stationary. The birds are, however, often quiet on the 



