422 NORTH AMERICAN BIRDS. 



usual ; but in the Cypselino: they are 2, 3, 3, and 3, as shown in the accom- 

 panying cut borrowed from Dr. Sclater's masterly memoir on the Cypsdidm, 

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

 arrangement here presented. 



Left foot of ChcBtura zonaris. Left foot of Panyptila melanoleuca. 



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. 



Shafts of tail-feathers projecting beyond the plumage . Chcetura. 

 Shafts not projecting, {Nephoscetes) .... Cypseloides. 



Tail-feathers not spinous ....... CollocaUia. 



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 

 CollocaUia make the " edible bird's-nests " which are so much sought after in 

 China 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 Cypselidm have the salivary glands highly developed, and use the secre- 

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

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



There are many interesting peculiarities connected with the modification 

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

 common Chimney Swallow will be referred to in the proper place. Panyp- 

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

 the 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 on a kind of shelf near. the top. Glimtu.ra poliura of 

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

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



