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136 THE CONDOR Vor,. XI first trip we visited the immense colony of ir?elecanus californicus on North Island and Phalacrocorax penicillalus on Middle Island. On June 1st, we campt in the heart of the Auklet colony, and within a few yards of the colony of Larus occidenlalis. Besides birds we found reptiles in abundance on South Island and a mouse (Peromyscus), species unknown, very abundant on North Island. Mr. Beck col- lected a large series of lizards, and six rattle snakes and Mr. Ad. van Rossem one gopher snake. Acknowledgements are due Mr. Henry B. Kaeding for identification of doubt- ful species and general help on the biota of the Islands. The following is a complete list of the birds we found on the Islands, covering a period from April 4 to June 6. Ptychoramphus aleuticus. Cassin Auklet. North Island was completely covered with burrows of this species. During our week's stay Mr. Lamb and I ex- plored it carefully and the approximate census was between six and eight thousand burrows. On April 6 most of the burrows were empty, only one out of every five that we examined being occupied, but on June 1 nearly every burrow examined contained either young in the down or incubated egg. A. few fresh eggs were found. The nests most accessible were in the rocky soil in the Pelican colony where simply overturning a rock would disclose the egg. We found the eggs some- times covered with soft sediment, a method of concealment perhaps. The eggs were smooth, and varied in color from a pure white to dark brown from nest stains. There was usually one egg to a burrow; in a few caqes we found'two birds occupy- ing the same burrow. The burrows ranged in length from eight inches to five feet. The nest was usually lined with dry grass and frequently small sticks and feathers. Brachyramphus hypoleucus. Xantus Murrelet. The first note of this species nesting on the Coronados was made by Mr. Beck on April 4, 1908. He found two sets high up on the side of South Island. I collected two females and one male June 1, 4, and 5. A complete account of this species as nesting on Los Coronados Islands is found iu the CONDOR, Vol. XI, no. 1, pages 8 and 9. Larus occidentalis. Western Gull. Hundreds of Western Gulls were flying over the Pelican colony on April 16 and would destroy the eggs at every opportun- ity. They had not yet begun to lay, but during the week of May 31 to June 6 nearly all the nests contained young in the down or incubated eggs. Larus californicus. California Gull. Three birds of this species were noted April 6 near South Island. Puffinus opisthomelas. Black-vented Shearwater. A small flock was seen rest- ing on the water off South Island April 8. 0ceanodorma socorroensis. Socorro Petrel. Found nesting on Middle Island. Several adults collected and one fresh egg secured by Mr. Lamb June 4. Phalacrocorax auritus albociliatus. Farallone Cormorant. Nesting scattering-. ly in the California Brown Pelican colony on North Island. Adults in full breeding plumage were taken. On June 1 we found fifteen pairs nesting (incubated eggs) in the Pelican colony which was then practically deserted. Phalacr0c0rax penicillatus. Brandt Cormorant. This was by far the most abun- dant Cormorant on the islands. On April 8 we found a colony of over one hundred pairs nesting on Middle Island. The nests were made of dried seaweed and covered with guano. The sets ranged from three to five, four being the commonest. Only one set of five was noted. On June 1 we located a colony of ninety-five pairs on an outlying rock on the west end of North Island which joins the main island by a