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May, 1916 A VISIT TO HAT AND EGG ISLANDS 117 southwest side of the island, where the birds were the most abundant and the view less obstructed by rocks and vegetation. By actual count of the birds in figure 36, there were found to be 391 on the wing above the sky line and 330 below. Allowing a ten percent increase in the latter to account for the birds that are concealed behind the rocks and vegetation, there would be a total of 754 birds that were within the field of the camera. Taking as a very con- servative estimate that this picture would include one-tenth of all the gulls that inhabit this island, we get 7540, or practically eight thousand as an esti- mate of the gull population. Other estimates, however, range from 15,000 to 20,000. There were, perhaps, two thousand White Pelicans, some four hundred Great Blue Herons, and about fifty Caspian Terns. Thus summarizing, we would get the following as an approximate estimation of the bird population of Hat Island. Considering the small size of the island. it will be seen that its population is relatively dense. - 7 Fig. 37. NESTING GULLS. PRACTICALLY ALL THE gIRDS -?RE FACINO THE SUN. California and Ring-billed Gulls .......... ? .................................................... 8,000 White Pelicans .............................................................................................. 2,000 Great Blue Herons ........................................................................................ 400 Caspian Terns ................................................................................................ 50 Total ........................................................................................ 10,450 C.?sPJ.?N Tr?RN.--There were very few of the beautiful Caspian Terns; twenty-five pairs would probably inehde all that our party saw on the island. There was a small colony of about twenty that nested on the beach near the point where we had inadvertently pitched our camp. Some of the eggs examined in the colony were fresh, and others partly incubated. All the nests were located in a space not more than twenty feet square. The nests were built each in a small hollow about two inches deep by six inches in diameter, and were erudel? lined with short sticks. The eggs in alt eases were two in number. The outline of the egg showed a very pointed oval. They normally have a pale blue background and are mottled with a brownish pigment. The ?nottles or blotches are larger and more vivid on the large-end of the egg.