NORTH AMERICAN BIRDS. 31 



the Murre and upon young Eider ducks.* The eggs of this Gull vary from a bluish- 

 white or olive-gray to a deep yellowish brown, and are irregularly spotted and 

 blotched with reddish-brown and .lilac of different shades. The sizes vary from 

 2.70 *■} 3.02 long by 2.05 to 2.25 broad. 



48. SLATY-BACKED GULL. Larus schistisagus (Stejn.) Geog. Dist.-^North 

 Pacific, chiefly on the Asiatic side; Herald Island, Arctic Ocean, and Alaskan coast 

 of Bering Sea. 



Dr. Stejneger says: "Among the specimens of gull collected by me on the 

 dommander Islands is a very dark-mantled large species,, somewhat intermediate 

 between L. marinns and L. dacMnnansi although in general aspect much nearer to the 

 former, and when on the wing indistinguishable from it. The occurence of this 

 new species in the Kamtschatkan waters easily explains the abnormality in the 

 alleged distribution of Larus marinvs, as it is almost certain that all North Pacific 

 references to the latter species really belong to the present forro."t 



49. WESTERN GULL. Larus occidentalis Aud. Geog. ,Dist.— Pacific coast 

 of North America, breeds from Southern California northward. 



The most abundant species of gull on the California coast, breeding on all suit- 

 able islands. It is the only gull which breeds on the Farallons. Mr. Emerson 

 states that on these islands the nest is built either on high ridges or low places near 

 the shore. The material used is a dry, rank weed; with this they construct their 

 rather bulky nest and repair or rebuild it each year. Mr. Barlow remarks that this 

 gull nests chiefly in colonies on the Farallons, on level portions, although a few 

 pairs may be found almost anywhere. The nests are loose affairs of Farallon weed 

 and measure a foot across. Usually they are very shallow and are given shape by 

 the hollows in which they are constructed. t ■ Of their general habits Mr. Bryant 

 says; "The gulls are indiscriminate feeders; in addition to their usual articles of 

 diet, they subsist largely upon eggs during the ummer. They do not eat the eggs 

 of their own species, nor do th3y trouble the cormorants after the murres have com- 

 menced laying. Sea urchins, crabs, young murres and rabbits, and fish stolen from 

 the cormorants' nests are eaten. Not being quick enough to swoop upon the rabbits, 

 they catch them by patient watching at their burrows, and will persevere for fifteen 

 minutes to swallow a squealing young rabbit,, and finally fly away with the hind feet 

 protruding. The dead bodies of murres are also eaten; they detach pieces of flesh 

 by backing away and dragging the body, meanwhile shaking their head, till a piece 

 breaks off." The eggs are deposited as early as the first part of May on the Faral- 

 lons, and laying is sometimes continued into July. The usual complement is three; 

 but from constant robberies by the eggers, who collect eggs for the Sin Francisco 

 market, often only two are laid. The same variation of ground-color and markings 

 are to be found in these eggs as is common to all those of the gulls; light grayish 

 olive, clay color, bluish-white and deep yellowish-brown, spotted and blotched with 

 umber-brown, blackish and lilac of varying shades. The average size of fifty speci- 

 mens is, 2.76x1.94; the largest 2.99x2.01; the smallest 2.56x1.89. 



50. SIBERIAIT G.ULL. Larvs affinis Reinh. Geog. Dist.— Greenland; Asia; 

 Europe, . southward in winter to North Africa. 



* Ornithologist and Oologlst, Vol. XTI., p. 17. 



t The Auk.. I., 231. 



t The Museum, T., p. 39. 



