4. Melospiza melodia common Song Sparrow One nest was found with an infertile egg and a young bird about ready to leave the nest. This nest was completely lined with white breast feathers of the Western Gull. With the absence of hair, these island birds apparently utilize feathers in place of the universal hair nest lining of all mainland races. At least two other flying young were noted being attended by parent birds. In no case was more than one young present in any family group. MAMMALS Phoca vitulina Harbour Seal One small two foot individual was photographed and released on North Island and 22 others were counted on Center Island. Zalophus californicus California Sea Lion A count of 589 animals was made around both islands. Both bulls and cows were present, but no harem activities had as yet begun. One yearling was seen nursing. Mus musculus House mouse Numerous on North Island during nocturnal hours; none was in evidence during the daylight survey. Field Summary Los Coronados Islands: species # Banded # Collected # Sera Samples # Returns Black Petrel - 20 5 -