THE WORLD'S BIRDS. 159 



CAPTIVITY. They have done well in the London 

 Zoological Gardens, and reared young there. 



DISTRIBUTION AND PRINCIPAL SPECIES. Two species 

 only (Eurypyga helias and E. major) are known, 

 much like each other, inhabiting South America 

 and living by the waterside in wooded places. 



SWIFTS (Cypselidce). 



DIAGNOSIS. Swallow-like birds, with the first toe the 

 smallest, and only ten tail-feathers (as against twelve 

 in swallows}. 



SIZE. From that of a blackbird to that of a tit 

 (allowing for shape). 



FORM. Much as in swallows, with small bill and feet 

 and long wings. Bill with corner of mouth coming 

 below eye ; feet with very short shanks, usually 

 feathered, and never scaled, first toe smallest and 

 often directed inwards and forwards instead of 

 backwards ; wings very long ; tail long or short, 

 forked, square or rounded ; in latter case often 

 with spinous tips to quills. 



PLUMAGE AND COLOURATION. Black and white com- 

 monly, but sometimes showing brown or metallic 

 blue and green ; usually no sex-difference, and no 

 seasonal change. Fledged young much like adults, 

 but with light edgings to the feathers. 



YOUNG. Naked and helpless, fed by parents. 



EGGS. One to four ; pure white, elongated in form: 



NEST. Various, usually on rocks or buildings, some- 

 times on trees ; made more or less of the birds' 

 sticky saliva. 



INCUBATION. Eighteen days. 



FOOD. Insects, usually captured on the wing. (I 

 have, however, once seen a Collocalia picking in- 

 sects off a tree as it swept past.) 



GAIT. An awkward crawling walk ; they are planti- 



