936 



SWIFT 



markable nests consist essentially of mucus, secreted by the salivary 

 glands above mentioned, which dries and looks like isinglass. Their 

 marketable value depends on their colour and purity, for they are 

 often intermixed with feathers and other foreign substances. The 

 Swifts that construct these " edible " nests form a genus Collocalia, 

 of which the number of species is uncertain ; but they inhabit 

 chiefly the islands of the Indian Ocean from the north of Madagascar 

 eastward, as well as many of the tropical islands of the Pacific so 

 far as the Marquesas, — one species occurring in the hill-country of 

 India. They breed in caves, to which they resort in great numbers, 

 and occupy them jointly and yet alternately with Bats — the 

 mammals being the lodgers by day and the birds by night.^ 



The genus Cypselus, as noted by AVillughby, with its American 

 ally Panyptila, exhibits a structure of the foot not otherwise ob- 

 served among birds. Not only is the hind-toe constantly directed 

 forwards, but the other three toes depart from the rule which 



Cypselus. 



ACANTHVLLIS. 



(After Swainson.) 



Macropteryx. 



ordinarily governs the number of phalanges in the Bird's foot, — a 

 rule which applies to even so ancient a form as Archmopteryx (FossiL 

 Birds, p. 278), — and in the two Cypseline genera just named the 

 series of digital phalanges is 2, 3, 3, 3, instead of 2, 3, 4, 5, which 

 generally obtains in the Class Aves. Other Swifts, however, do not 

 depart from the normal arrangement, and the exception, remarkable 

 as it is, must not be taken as of more value than is needed for the 

 recognition of two sections or subfamilies admitted bv Mr. Sclater 

 in his monographical essay on the Family (Proc. Zool. Soc. 1865, 

 pp. 593-617^. Mr. Hartert {Coi. B. -Br. Mus. xvi. pp. 434-518) 

 recognizes thi'ee subfamilies with nine genera and 78 species. 

 Their geographical distribution is much the same as that of the 

 Hirandinidx (Sw ALLOW, p. 926) ; but it should be always and most 

 clearly borne in mind that, though so like Swallows in many respects, 

 the Swifts have scarcely any part of their structure which is not 

 formed on a different plan ; and, instead of any near affinity existing 

 between the two groups, it can scarcely be doubted by any un- 



^ Mr. H. Pryer has given one of the latest accounts of some of these caves 

 in North Borneo {Froc. Zool. Soc. 1885, pp. 532-538), whicli may be read to 

 advantage. 



