422 NORTH AMERICAN BIRDS. 



usual ; but in the Cypsdina; they are 2, 3, 3, and 3, as sliowii in the accom- 

 pau\iiig cut borrowed from Dr. Sclater's masterly memoir ou the Cypsdidw, 

 (Pr. Zool. Soc. London, 1865, 593), which also serves as the basis of the 

 arrangement here presented. 



Left foot of Chmma zonaris. Left foot of Panyplila melanoUuca. 



Cypselinae. Tarsi feathered ; phalanges of the middle and outer toes three 

 each (instead of four and five). Hind toe directed either forward or to one 

 side, not backward. 



Tarsi feathered ; toes bare ; hind toe directed forward . . . Cypselus. 

 Both tarsi and toes feathered ; hind toe lateral .... Panyptila. 

 Chaeturinae. Tarsi bare; phalanges of toes normal (four in middle toe, 

 five in outer). Hind toe directed backwards, though sometimes versatile. 

 Tarsi longer than middle toe. 

 Tail-feathers spinous. 



Shaft.s of tail-feathers projecting beyond the plumage . Chcetura. 

 Shafts not projecting, (Xephceceies) .... Cypseloides. 



Tail-feathers not spinous Collocaltia. 



Tarsi shorter than middle toe Dendrochelidon. 



The Swifts are cosmopolite, occurring throughout the globe. All the 

 genera enumerated above are well represented in the New "World, except 

 the last two, which are exclusively East Indian and Polynesian. Species of 

 CoUocaJUa make the " edible bird's-nests " whicli are so much sought after in 

 Cliina and Japan. These are constructed entirely out of the hardened saliva 

 of the bird, although formerly supposed to be made of some kind of sea- weed. 

 All the Cypselidcc have the salivary glands highly developed, and use the secre- 

 tion to cement together the twigs or other substances of which the nest is con- 

 structed, as well as to attach this to its support. The eggs are always white. 



There are many interesting peciiliarities connected with the modification 

 of the CypselidcB, some of which may be briefly adverted to. Those of our 

 common Chimney S\\'allow will be referred to in the proper place. Fanyp- 

 tila sandi-hieronymm of Guatemala attaches a tube some feet in length to 

 tlie under side of an overhanging rock, constructed of the pappus or seed- 

 down of plants, caught flying in the air. Entrance to this is from below, 

 and the eggs are laid ou a kind of shelf near the top. Chcetura poliura of 

 Brazil again makes a very similar tube-nest (more contracted below) out of 

 the seeds of Trixis dwaricatu, suspends it to a horizontal branch, and covers 



