ORNITHOLOGY OF GUADALUPE ISLAND. 291 



I have found but two exceptions to the extent of black on 

 the ends of the retrices. One in the case of a female rufipi- 

 leus, in which the black reaches only about 38 mm. from 

 the ends of the feathers, arid the other a female cafer (jor- 

 merly Jiybridus) in which the black extends about 57 mm. 

 In typical rufipileus, the black covered about 63 mm. of the 

 ends. This I found to be the most constant difference. 



The absence in every case of a definite or clearly defined 

 cheek-patch in the females, and also the absence of mar- 

 ginal light spots on the outer web of the exterior retrices in 

 both sexes, will aid in determining this species. These 

 spots, although rarely if ever wanting in typical cafer are 

 seldom or never found in rufipilens. An apparent exception 

 is found in a male from Guad^upe Island, which has a 

 slight touch of light on the webs. 



10. Micropus melanoleucus. 



WHITE-THROATED SWIFT. On January 12, a flock of about 

 fifty swifts passed near camp, moving towards the north- 

 east. They flew in every direction, but kept well together, 

 and gradually ascended to a higher altitude. I could not 

 get near enough to distinguish any characteristic markings. 

 They were again seen during a few hours of sunshine on the 

 15th, but only at a distance. 



A storm of wind, rain and dense fog, which had lasted 

 almost without interruption for twelve days, cleared away 

 January 21, and with the welcome and returning sunshine 

 came the swifts. They were flying lower than usual, and 

 occasionally one would chatter as he swept above the tree- 

 tops. The birds were feeding upon a species of slender 

 black fly, with which the air was swarming, and although 

 dispersed for a time by the report of a gun, they soon re- 

 turned to their feast. As late as April, they were still on 

 the island, but only a few at a time were seen, the flock hav- 

 ing evidently separated, although not apparently paired off. 

 One calm day, about a dozen birds were seen skimming low 

 over the grass in the manner of swallows. As far as my ob- 



