BIRDS 



247 



and the skin back of the base of the lower mandible are purplish- 

 black. 



We found this species nesting on Culpepper and Wenman in De- 

 cember, on Hood in May and on Tower in June; but it- was seen 

 nowhere else in the archipelago. Hence it is coincident in its range 

 at the Galapagos with Sula variegata. 



At Wenman Island we found it abundant in December on the small 

 islet off the north side of the main island. Nests were numerous and 

 were always placed in the low bushes that cover most of the island. 

 The birds were never observed to alight anywhere else than in these 

 bushes when they came to the island. The most common sound they 

 uttered consisted of a short series of hoarse, guttural notes. 



On Tower, also, they always nested in the bushes. Here the nests 

 were placed four or five feet above the ground and consisted of twigs 

 somewhat woven together into a circular form with a shallow depres- 

 sion above. Sometimes a few dry leaves were placed in the bottom of 

 the cavity. The incubating bird holds the single egg between her 

 feet. None of the nests at this time on Tower Island contained 

 young birds. 



This habit of nesting in trees or bushes distinguishes this species 

 from all the other Sulas of the eastern Pacific, and the species occurs 

 on all the tropical islands of this region except Clipperton, where 

 vegetation is is wholly lacking. 



MEASUREMENTS OF ADULT SPECIMENS OF Sula 



webstert. 



On Culpepper, Wenman and Tower, birds in the white plumage 

 were very scarce compared with the number of those in the immature 

 brownish plumage. The majority of nests containing eggs or young 

 birds we found occupied by one of these fully grown but brownish 

 birds. These individuals were certainly immature, but must have 



