30 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



juttings of rock on the walls of the cliffs and of caves, and 

 sometimes they were built on top of old nests. They were 

 all damp, and about two-thirds of them contained eggs, some 

 of which were incubated. Of eight eggs collected, two were 

 fresh, while in the remaining six incubation had begun. With 

 this species one egg constitutes a clutch. The owners were 

 all lacking in timidity and several were caught by hand. 



On September 1, 1905, the Clipperton Noddy was met with 

 about thirty miles south of Cocos Island, Costa Rica, and the 

 following day one was captured. 



During our stay at Cocos Island in the first half of Sep- 

 tember, this species was found commonly along the shore 

 line between Chatham and Wafer Bays. Three were seen fly- 

 ing up the fresh-water creek at Wafer Bay. They roosted 

 in the trees as well as on the rocks along the shores. Indi- 

 viduals often circled about the small boat four or five times, 

 keeping too close for shooting. Like the Noddy this species 

 is quite readily decoyed to wounded birds. So far as noted 

 neither species dives for its food. In two instances Man-o'- 

 war Birds were seen in pursuit of Clipperton Noddies. 



Messrs. Snodgrass and Heller^ report this species as nesting 

 in the tall trees near Chatham Bay in July. During our stay 

 in September, young, a-wing, appeared to be more numerous 

 than adults, evidencing that the breeding-season had passed. 

 The two ornithologists referred to above report only imma- 

 ture birds at Clipperton in November. 



The specimens in the Academy's series agree very well with 

 the descriptions^ of the adult and immature males given by 

 Messrs. Snodgrass and Heller. There seem to be no charac- 

 ters, aside from length of culmen, which differentiate the males 

 and females, either adult or immature. All of the young birds 

 taken were able to fly, and all were captured at Cocos Island, 

 with the exception of one secured on Clipperton, August 10. 



Of a series of thirty specimens taken on Clipperton on 

 August 10, one (No. 1593 C. A. S.) is completing the juvenal 

 plumage, for the primaries and rectrices are yet in an imma- 

 ture state. Growing feathers are also to be seen in both the 

 dorsal and ventral tracts. Two specimens, Nos. 1525 and 

 1548, are immature, and are going through a belated first 



^Proc. Wash. Acad. Sci., v. 4, p. 510. 

 Hbid, p. 509. 



