This species is well known, by sound, in nearly all parts of its range, but comparatively few ever observed the bird, and probably the greater number mistake the Nighthawk for this species. The two species can readily be distinguished at a distance by the absence of any pronounced white marking in the wings, and by the white tips to the outer tail feathers in the present species, while the Night Hawk has a prominent white band across the tail, but the top is black, and the tail slightly forked. The Whip-poor-will, rarely leaves its place of concealment before dark, and is never seen flying about cities, as are the Nighthawks. In their pursuit of insects, they glide like a shadow over fields and woods, their soft plumage giving forth no sound as their wings cleave the air. Until late at night, their whistling cry "whip-poor-will," repeated at intervals, rings out in all wooded hilly districts. Their two eggs are deposited on the ground among dead leaves, generally in dense woods. They are grayish white or cream color marbled with pale brown and gray, with fainter markings of lilac. Size 1.50 × .85. [Illustration 265: Grayish white.] [Illustration: Chuck-will's-widow.] [Illustration: Creamy white.] [Illustration: Whip-poor-will.] [Illustration: right hand margin.] Page 264 417a. STEPHEN'S WHIP-POOR-WILL. _Antrostomus vociferus macromystax._ Range.--Arizona and New Mexico, south through the tableland of Mexico. This sub-species is slightly larger and has longer mouth bristles than the eastern bird. Their nesting habits are the same and the eggs differ only in averaging lighter in color, with fainter markings, some specimens being almost immaculate. 418. POOR-WILL. _Phalænoptilus nuttalli nuttalli._ Range.--United States west of the Mississippi, breeding from Kansas and northern California northward to Montana and British Columbia. This handsome species is the smallest of the family, being under 8 inches in length. Its plumage is mottled black, white and frosty gray, harmoniously blended together. They can easily be distinguished from all other Goatsuckers by their size and silvery appearance. They nest on the ground, either placing their two eggs upon a bed of leaves or upon a flat rock. The breeding season is from the latter part of May through July. The eggs are pure white and glossy; size 1.00 × .75. 418a. FROSTED POOR-WILL. _Phalænoptilus nuttalli nitidus._ Range.--Texas and Arizona, north to western Kansas. This variety is like the last but paler, both above and below. Eggs indistinguishable from those of others of the genus. 418b. DUSKY POOR-WILL. _Phalænoptilus nuttalli californicus._ Range.--A darker race found on the coast of California, having the same nesting habits as the others. The egg figured is of this species. Data.--Los Angeles, Cal., June 24, 1900. 2 eggs on the ground at the foot of an oak tree on the side of a hill. Collector, F. M. Palmer.