GOATSUCKERS. 305 



and structure. They may differ, however, in the latent power 

 of producing distinct eggs ; they may differ less in the latent 

 instinct of building different nests, or still less in the latent 

 power of producing eggs, many of which contain the germs of 

 very distinct male birds. Hence the freshly laid eggs of two 

 species may be indistinguishable except in latent, undeveloped 

 features, though, since like produces like, they may be identi- 

 fied through the parent birds. 



NOTE. The third order, PSITTACI (Parrots and their 

 allies), is not represented in New England. Its members 

 have toes in pairs, and an essentially raptorial bill. (See 

 Chap. III.) 



20. The CAPRIMULGID^J (or Goatsuckers, of which 

 the American species are typical, and belong to the subfamily 

 Caprimulgince) and the CYPSBLID^B (or Swifts, 21, 

 pi. 1, fig. 23) form a natural group * possessing the following 

 features : gape, extensive, and about six times as long as the 

 culmen (or upper outline of the bill) ; feet, small and weak ; 

 primaries, ten ; tail-feathers, ten. The Goatsuckers may be 

 distinguished from the Swifts by the more or less bristled 

 bill, the feet slightly webbed at the base, and the elevated 

 hind toe. This last feature, however, also belongs to the 

 Chceturince, a subfamily containing the Chimney " Swallows," 

 and differing further from the true Swifts in having unf eath- 

 ered tarsi. The Chceturce ( 21, I) have mucronate tail- 

 feathers, in which the shaft projects beyond the webs. (PI. 1, 

 fig. 22.) 



The Swifts probably possess powers of locomotion superior 

 to those of any other living creatures. With their long, 

 pointed wings, they are said to fly sometimes at the rate of 

 two hundred and fifty miles an hour. They are strictly in- 

 sectivorous and migratory, and more or less colonial. " They 

 never perch, but many resort to hollows, as in trees, for the 



* Dr. Shuf eldt regards the Swifts as alone among modern systematists. 

 most nearly related to the Swallows, W. B. 

 but in this opinion he stands nearly 



