JAN., 1909. BIRDS OF ILLINOIS AND WISCONSIN CORY. 525 



' A specimen labelled henryi in the Field Museum collection from 

 Mr. C. K. Worthen taken at Fox Island, Missouri, is much nearer 

 sennetti, and judging from specimens available for examination, the 

 occurance of henryi, at least in Illinois, requires further confirmation. 



Sennett's Nighthawk has been recorded from Iowa (Bartsch, Auk, 

 1899, p. 86), Minnesota (Lano, Auk, 1898, p. 54), and has been found 

 not uncommon in North Dakota (Bishop, Auk, 1896, p. 134). 



The three forms may generally be recognized by the following 

 characters, although there is often much variation in plumage: 



C. virginianus: General plumage, dark, the black predominating 

 on upper parts; under parts, barred with black and white in about 

 equal amounts; very little rufous shown anywhere. 



C. v. sennetti: Much paler; grayish white and brown, on upper 

 parts; under parts, white, barred with narrow imperfect dark bars, 

 the white predominating; very little or no rufous noticeable any- 

 where. 



C. v. henryi: Upper plumage showing considerable tawny rufous 

 marking; under parts, marked with tawny white and dusky black. 



Suborder CYPSELI. Swifts. 



Family MICROPODI D^. Swifts. 



Swifts are often mistaken for swallows by those unfamiliar with 

 birds, but are widely separated from them both in habits and struc- 

 ture. The sharp spines extending from the tail feathers and sooty 

 brown plumage will readily distinguish the species which occurs in 

 eastern North America. 



A peculiar feature of this family is the wonderful development 

 of the salivary gland, enabling the birds to salivate the material of 

 which the nest is formed, not only sufficiently to glue it together but 

 to attach it to a rock or brick wall, often-times a chimney. The young 

 are fed by regurgitation. The edible birds' nests of China are made 

 by birds of this family. About 50 species are known from various 

 parts of the world. 



