3 2 Grinnell and Daggett, Birds of Coronados Islands \u^ 



the Black Petrel, for an adult was never found in a burrow with a young 

 bird more than a day or two old. But in some sixteen of the burrows 

 there was an egg, in which case one of the parent birds was brooding, 

 either male or female, indifferently. The Socorro Petrels' eggs were 

 white, and either immaculate, or showing a faint ring of lavender and 

 cinnamon dots around the larger end. Nine examples average, in inches, 

 1. 20 X 0.90, or, in millimeters, 30.5 X 23. 



Among our skins of O. socorroensis are four which show more or less 

 white on the rump. One of these {$ , No. 4331, Coll. F. S. D.) has the 

 lateral upper tail-coverts from base to tip pure white ; so that the rump 

 may be described as white with a dusky median stripe. This specimen is 

 in this respect not distinguishable from some examples of O. leiicorhoa^ 

 and in fact the only difference apparent to us is a scarcely perceptible 

 darker shade to the general plumage. Another specimen (No. 4333, Coll. 

 F. S. D.) has only the outer webs of the lateral rump feathers whitish. 

 Another (No. 5246, Coll. J. G.) has a still more restricted edging of 

 white; while one more (No. 4322, Coll. F. S. D.) has merely a trace of 

 pale edging. All the rest of our series of twenty-four specimens have the 

 rump uniform sooty brown like the back. This variation toward the 

 white-rumped condition has been noted in this species before (Anthony, 

 Auk, XV, 1898, pp. 37, 38), and seems to be purely individual. Yet it may 

 reasonably serve to indicate probable recent origin from a widespread, 

 white-rumped ancestor like O. leucorhoa^ which O. socorroensis otherwise 

 approximates so closely. A comparison of specimens of O. socorroensis 

 with the fine series of O. homochroa in the California Academy of Sciences 

 collected by Leverett M. Loomis on the Farallones, shows the differences 

 between these two forms to be slight but constant, consisting in some- 

 what paler color and smaller size of the latter. 



6. Sterna forsteri. Forster Tern. — Several were seen flying about 

 the launch while we were approaching and yet some distance from South 

 Island. 



7. Phalacrocorax auritus albociliatus. Farallone Cormorant. — 

 Several pairs were breeding on the south end of North Island. The nests 

 were built up quite substantially on rocks and bushes near the summit of 

 the ridge. Two nests contained two and three eggs respectively, while 

 several others had small young. This species builds separately from the 

 Brandt Cormorant, none of which were seen in company with the former. 



8. Phalacrocorax penicillatus. Brandt Cormorant. — This was the 

 most abundant cormorant in the vicinity, and many had evidently nested 

 around the sides of North Island, where numerous empty nests were noted. 



9. Pelecanus californicus. California Brown Pelican. — Large 

 numbers were always to be seen about the islands, either roosting on out- 

 lying rocks or going and coming in undulating lines from their feeding 

 grounds somewhere up the mainland coast. A big colony had bred on 

 North Island, for nests were numerous there at the south end. Most of 

 the young were full grown and able to fly, but a few were found still in a 



