152 THE CONDOR VoL. XI and here that the majority were nesting, altho there were about nine pairs on another rock lying fifty yards to the north, and a few scattered individuals which I will mention later. As our boat neared the island a few more, beautifully plumaged adults came out to greet us, and when I climbed over the top of the cliff which surrounds the rock, I came in view of the entire colony. The rock was about twenty-five feet high and fifty by one-hundred-and-fifty feet across, with a plat of.coarse bunch grass a foot high in the center, and along the edge a barren strip of white rock broken up here and there with crevices and boulders. The rock contained thirty-one pairs of breeding birds, ascertained after a careful count. The birds in the nesting grounds behaved in much the same manner as the Western Gulls, but were tamer, swooping down within a foot of my head and alighting nearby, while I was photographing in the colony. Their cry was an oft-repeated "cow-awk", "cow-eek", given when high in the air, and a rapid guttural "caw-ca-ca-ca" when hovering near the nest. No adults were noted eating other gulls' eggs, nor did I see them disturb the Blue-looted Boobys (?S'ula nebouxii) which were nesting on a nearby island. They were beautiful with graceful flight and striking plumage. The plumage of the adult birds is too well known to warrant a description
here. Of the series now in my collection (one skin of which was taken by Mr.
Chester Lamb, my companion and co-worker on this trip) both sexes are identical, with pure white heads. One downy young was taken on my second visit to the rock, three days later, April 14. At this age the bird shows a soft downy coat, of a light creamy color on the underparts, which merges into vinaceous cream buff on the mantle and nape; crown and occiput slightly speckt with black; nape clear cream; entire back and rump heavily spotted with blackisl? slate color; wings, under side plain white, upper parts spotted with blackish; flanks pale cream spotted with blackish. Measurements in millimeters, length 148, wing 30, bill 17. Bill hookt, nostril near middle, section on upper mandible back of nostril dark, remainder light brownish. A few immatures were seen flying near the rock. Their entire plumage was soft, sooty gray, except blackish on tail and wing quills. A. cursory survey of the rock showed that it was steep on all sides. The birds undoubtedly preferred the level ground for a nesting place, as only one set was found on this cliff. The nests were located usually between boulders, or nestled down in the bunch grass in the center of the rock. Those in the grass were usually well made of sticks, dry grass .ai?d weeds, and sometimes with a slight lining of feathers. They were much better:made .and more compact than those of the Western Gull. Several nests in my collection still show their or!ginal shape and construction; also retain the strong odor pec. uliar to these birds on their nesting grounds. A few sets were found with almost no nest, simply a cup-shaped cavity scantily lined with shells and a stick or two. The nests were well scattered about over the rock, no close grouping being evident. The measurements of the nests average, in inches: out- side width 10; depth 2. No other species of Gull was seen in company with the Heermann Gulls, and none within hundreds of miles of these islands. The eggs of this species are unlike those of other Gulls, and can be distinguisht with a series.. My series show the usual variation in color and size so common in eggs of the genus Larus. In shape they are in general identical with others of this genus. Sets vary considerably in size, and average smaller than those of JLarus occldentalis. The first visit to the rock was on April 11. At this time about one-
