174 LIFE HISTORIES OP NORTH AMERICAN BIRDS. 



exposed to the rays of the sun, or near the base of some desert shrub, which at 

 best furnishes but httle protection from the intense heat, and I have found its 

 eggs on tlie parched gravelly mesas of southern Arizona, miles from the nearest 

 water. Their favorite breeding resorts here are the dry, barren table-lands, 

 the sides of canyons, and the crests of rocky hills. Although not absolutely 

 certain, I believe the two eggs are deposited on alternate days, and incubation 

 begins with the first egg laid. They are exceedingly difficult to detect on 

 account of their similarity in color to their general surroundings, which usually 

 harmonize very closely. The shell is strong, close grained, and rather glossy, 

 while in shape the eggs are more variable than those of our other Nighthawks, 

 ranging from oval to elliptical oval, and again to elliptical ovate. The ground 

 color varies from pale gray (a sort of clay color) to pale creamy white, with a 

 faint ijinkish tint. This latter phase of coloration is rather unusual however. 

 The whole surface is minutely marbled, speckled, or rather peppered, with fine 

 dots of different shades of grays, lilac, and a few darker and coarser markings 

 of fawn color, slate, and drab. Occasionally a specimen is found which, to the 

 naked eye, appears entirely unmarked; but on more careful examination a few 

 dark spots, mere pin points, can readily be noticed. They are much lighter 

 colored than the average eggs of our other Nighthawks, and readily distinguished 

 from these on this account, as well as from their smaller size. 



The average measurement of fifty-five specimens in the United States 

 National Museum collection is 26.84 by 19.61 millimetres, or about 1.06 by 0.77 

 inches. The largest egg of this series measures 29.72 by 21.08 millimetres, or 

 1.17 by 0.83 inches; the smallest, 23.11 by 18.03 millimetres, or 0.91 by 0.71 inch. 



Of the type specimens (all selected from sets of two) No. 24210 (PL 3, 

 Fig. 7), taken by Dr. C. Hart Merriam, on May 13, 1891, near St. Greorge, 

 Utah, represents an egg with a light ground color, and a peculiar and rare style 

 of markings. No. 24312 (PL 3, Fig. 8), collected near Brownsville, Texas, on 

 May 8, 1891, shows one of the darker and heavier marked styles. No. 25299 

 (PL 3, Fig. 9), from the same locality, taken May 16, 1892, represents a very 

 rmiform aaid evenly colored specimen, while No. 26351 (PL 3, Fig. 10), likewise 

 from the same locality, taken May 8, 1 892, represents about an average-colored 

 egg of this species. The last three types are from the Ralph collection. 



