CYPSELID^E. 163 



Nidification varies greatly, but all the Swifts lay elongate white 

 eggs, and in all the saliva is used to cement together the materials 

 of the nest and to attach it to some surface. In some forms of 

 Collocdlia the nest consists entirely of inspissated saliva. The 

 salivary glands are greatly developed, especially at the breeding- 

 season. The young are hatched naked. 



A single family. 



Family CYPSELID^E. 



Bill small, hooked at the end, gape very broad. Wings long, 

 the primaries greatly developed, curved ; secondaries very short. 

 Humerus very short. Feet weak, the first or hind toe is more or 

 less reversible, and all four toes are often directed forward in 

 some of the genera. 



This family is cosmopolitan, except that it does not occur in 

 Arctic or Antarctic regions. There are three subfamilies, thus 

 distinguished : 



a. Tarsus feathered ; three anterior toes (2, 

 3, 4), each with three phalanges ; wings 



extending far beyond tail Cypselince, p. 163. 



6. Tarsus generally naked ; second toe 

 with 3, third with 4, fourth with 5 

 phalanges as usual. 

 a'. Tarsus equal to middle toe or longer ; 



wings extending far beyond tail . . GTiceturince, p. 172. 

 V. Tarsus shorter than middle toe ; [p. 179. 



wings not extending beyond tail . . Macropterygince, 



Subfamily CYPSELIN.E. 



This includes the typical Swifts, in which the hind toe is 

 completely reversible, and the third and fourth toes have only 

 three phalanges each. Sexes always alike. Two genera are 

 Indian. 



Key to the Genera. 



a. Toes all directed forward as a rule CYPSELUS, p. 164. 



b. Toes in pairs; inner and hind toes directed 



inwards, the other two outwards TACHORNIS, p. 170. 



M2 



