Page:Condor18(3).djvu/28

 118 THI CONDOR Vol. XVIII It was in this colony that the piratical tendency of the gull was first observed. Owing to the proximity of our camp to the colony, the terns, which are shy birds, abandoned their nests. The gulls, which have little or no fear of man, and no compunction about egg stealing (of this we found ample evi- dence), raided this colony and destroyed a number of the eggs. The remainder were taken' by our party as specimens, as it was evident that they would other- wise be' destroyed. CALIFORNIA AND RING-BILLED GVLLs.--The nests of these birds'were found in all parts of the island though they were the most plentiful on the beaches of the south and west sides. An idea of their abundance may be gained from figure 37, which was taken on the south beach. It 'is of interest to note that all the nest- ing birds are facing in one direction, the east. Nests were found on all parts of the island, from the beach within a few feet of the water to the top-most ledge in the crown of the Hat; from the sandy beach to the nooks and crannies of the rocks, and under the greasewoods; two were even found in abandoned nests of the.' Great Blue Heron. They were in the parts of the island appropriated exclusively by themselves, and among the nesting colonies of the White Peli- cans and Great Blue Herons. For a description of the gulls' nests reference may be made to the description of the nest of the Caspian Tern, with the addi- tion that ttfose of the gulls were generally scantily lined with a few feathers and squirrel-tail grass. Very great diversity was seen in the individual eggs of different clutches. Some clutches were very light and sparsely mottled, others were almost entirely of a sooty brown color, the blotches covering the egg almost completely. A few had well defined streaks like the oriole's or red-winged blackbird's. One of the clutches was entirely different from the usual type in being blue in color and almost entirely unmarked. This can probably be explained by assuming some abnormal condition of the gland or duct that secretes the pigment, thus preventing the flow of the brown coloring matter with which the eggs are normally blotched. The eggs were a very pointed oval in outline and uniform in size. The clutches were practically completed at the time of our visit (May 16) and usually contained three eggs. Occasionally two and rarely .four were found. Only in exceptional cases wre young gulls found and these were but a day or so old. Figure 38 shows one of these cases. The pf-otective colora- tion of the young is here well shown by the likeness of the small elongated dots and background to the lights and shadows under vegetation. A query, however, might be interposed, for the light and shadow scheme is reversed in the bird, that is, the background on the gull is light while with the sur- roundings it is dark. An interesting condition was noted among the gulls that might be called involuntary parasitism. Several clutches were found with one egg that varied greatly in its markings from the other two. At first this was accounted for by assuming that the parent bird deposited an egg that simply varied in its mark- ings from the other two. Finally, however, there seemed to be so many of these cases that another explanation was sought, and what we believed to be the key to the true explanation was found in the presence of another clutch near by, with the identical markings of the odd egg. in the first clutch. We concluded, therefore, that the second gull had mistaken her neighbor's nest