, THE NIGHTIIAWK. 167 



( hih- two eg-gs are laid to a set (on alternate <lays) and incubation begins 

 with the first one deposited. The shell is strong, close-grained, and generall}- 

 moderately glossy; in shape the}' vary from elliptical ovate to elli])tical oval, the 

 former prevailing in tlie majority, one end Ijeing a triHe smaller tlian the otlier. 

 Their ground color is (piite variable, and ranges from a pale creamy white 

 through different shades of cream, olive buff, and olive gray, and tlic}- are i)ro- 

 fusely blotched and speckled with different shades of slate black, drab, smoke 

 and lilac g'ray, and tawu}^ oHve, mixed with lighter shades of pearl gray, lav- 

 ender, and plumbeous. In some specimens the markings are fine and uniform 

 in size, almost obscuring the ground color; in others they are less numerous, 

 but large and prominent. There is an endless variation in their markings. 

 Scarcely any two sets resemble each other closely, and I consider the egg- of the 

 Niii'hthawk one of the most difiicult ones known to me to describe sati.sfactorily. 



The average measurement of eighty-one specimens in the United States 

 National Museum collection is 29.97 by 21.84 millimetres, or 1.18 by 0.86 

 inches. The largest egg of this series measures 33.53 by 22.8(5 millimetres, or 

 1.32 by 0.90 inches; the smallest, 27.68 by 20.57 millimetres, or 1.09 by 0.81 

 inches. 



The type specimen, No. 9813 (PI. 3, Fig. 1), from a set of two taken 

 near Dubuque, Iowa, on May 28, 1865, by the Messrs. Blackburn, represents one 

 of the larger and heavier marked specimens. No. 24968 (PI. 3, Fig. 2), Ralph 

 collection, from a set of two taken by Dr. William L. llalph in Herkimer County, 

 New York, on June 24, 1891, represents a small specimen with an olive-gray 

 ground color and rather dark markings; while No. 20457 (PI. 3, Fig. 3), like- 

 wise from a set of two, Bendire collection, was taken 1)}' the writer near Fort 

 Klamath Oregon, on July 6, 1882, and rei)resents one of the lighter-colored 

 types. 



59. Chordeiles virginianus henryi (Cassin). 



WESTERN NIGHTHAWK. 



Chordeiles henryi. Oassin, Illustrations of the Birds of California, Texas, etc., I, 18.W, 2'Xi. 

 Chordeiles virginianus var. henryi CouES, Key, 1872, 181. 



(B 115, C 201(1, R 357<(, V 400, U 420a.) 



GEor.UAPnrcAL range: Western North America; north to central British Colnmbia 

 to about latitude 5.5^ and through the prairie districts of southern Alberta, Assiuiboia, and 

 western Manitoba; east in the United States to western MiniiesDta, Iowa, northern and 

 central Illinois, Ivausas, the Indian Territory, western aiul southern Texas; south over 

 the tabledands of Mexico, and in winter through Central America, over the greater part 

 of South America to Patagonia. 



The Western Nighthawk, a lighter-colored subspecies than the preceding, is 

 a common summer resident throughout a considerable portion of western North 

 America, but its range is likewise a rather irregular one. On the whole, it is 

 more of a prairie bird than the former, but it is by no means confined to the 

 plains alone; it appears to be equally at home on the more open, barren 



