1906.] NATURAL SCIENCES OF PHILADELPHIA. 177 



A MONOGRAPH OF THE GENUS COLLOCALIA. 



BY HARRY C. OBERHOLSER. 



There is perhaps no other group of Swifts that equals in general 

 interest the genus Collocalia. Some of the species build edible nests 

 wholly or partly of saliva which is secreted in large quantities by 

 salivary glands of unusual size; and the gathering and marketing of 

 these nests has in some places and at some times grown to a traffic of 

 considerable importance. 



Owing to the great similarity of many of the species, and the ob- 

 scurity of the characters separating them, the group is one of the most 

 difficult in the entire family Micropodidse. Published descriptions,^ 

 particularly those of the older authors, are often so brief and so lacking 

 in mention of really diagnostic characters that it is hard, sometimes 

 even impossible, to determine with certainty the form intended. For- 

 tunately, perhaps, the sexes, except in a very few cases, are practically 

 identical both in size and coloration. Notwithstanding the fact that 

 some authors have minimized the importance of difference in size, 



^ The most important papers on the genus are as follows: 

 HoRSFiELD, T., and Moore, F. — Genus Collocalia. A Catalogue of the Birds in 



the Museum of the Hon. East India Company, I, 1854, pp. 98-106. 

 Bonaparte, C. L. — Note sur les Salanganes et sur leur nids. Comptes Rendus de 



r Academie des Sciences de Paris, XLI, 1855, pp. 976-979. 

 Bernstein, H. A. — Beitrage zur naheren Kenntniss der Gattung Collocalia Gr. 



Nova Acta Academiae Leopoldinae Carolinae Naturae Curiosorum, XXVI, 1, 



1857, pp. 13-32. 

 Bernstein, H. A. — Ueber die Nester der Salanganen. Journal fur Ornithologie, 



1859, pp. 111-119. 

 Wallace, A. R. — On the Identification of the Hirundo esculenta of Linnaeus, 



with a Synopsis of the Described Species of Collocalia. Proceedings of the 



Zoological Society of London, 1863, pp. 382-385. 

 Gray, G. R. — A Synopsis of the Species of the Genus Collocalia, with Descriptions 



of New Species. Annals and Magazine of Natural History, Series 3, XVII, 



1866, pp. 118-128. 

 Salvadori, T. — Osservazioni intorno ad alcune Specie del Genere Collocalia, 



G. R. Gr. Atti delta R. Accademia della Scienze di Torino, XV, 1879, pp. 



343-350. 

 Hartert, E. — Collocalia. Catalogue of the Birds in the British Museum, XVI, 



1892, pp. 496-511. 

 Hartert, E.— Gen. Collocalia G. R. Gray. Das Tierreich, I, 1897, pp. 66-70. 

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