LIFE HISTORIES OF NORTH AMERICAN GULLS AND TERNS. 149 



It is well protected from the northwest wind, which prevails here in March 

 and April. At the time I arrived on the island immense numbers of these 

 gulls had congregated. They literally ci>vered the ground. They were so occu- 

 pied in their love making that they paid vei'y little attention to us. Their 

 cries deadened the cries of all the other birds, and they kept it up all through 

 the night. 



Xestinff. — The nest in all cases was simply a well-formed depression in the 

 ground with no lining whatsoever. There must have been over 15,000 Heermann 

 gulls nesting on this island. 



Mr. Pingree I. Osburn (1909) found a colony of Heermann's gulls 

 breeding " on a remote rock off the coast of the State of Jalisco, 

 Mexico, in about the parallel 18° N." He writes : 



The rock was about 25 feet high and 50 by 150 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 bowlders. The 

 rock contained 31 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. 



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 bowlders 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, and 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 original 

 shape and construction ; also retain the strong odor peculiar to these birds 

 on their nesting grounds. A few sets were found with almost no nest ; simply 

 a cup-shaped cavity scantily lined with sliells 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 — outside 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 first visit to the rock was on April 11. At this time about one-thii-d of 

 the eggs were heavily incubated. The remainder were in all the lesser stages. 

 The sets contain two and three eggs in about equal numbers, with a possible 

 majority of three. 



Effffs. — The eggs show the greatest variation in color. The general ground 

 color is pearl gray with a very slight creamy tinge. In some the ground color 

 is ashy gray and in others light bluish gray. All the eggs are spotted and 

 blotched, the markings showing no particular rule for location at one end or 

 the other. They have faint lavender spots, which are covered with smaller 

 but more distinct spots of grayish brown, umber, grayish blue, and dark 

 lavender. They are verj- rarely scratched with tine lines, but occasionally the 

 spots and splashes show a trend to a lengtliwise direction. A few examples 

 also have faint wreaths about the large end. Where this occurs the area 

 inside the wreath is usually void of heavy markings and decorated only with 

 faii:t irregular lavender spots. In extreme examples the eggs range from one 

 egg, which is indistinctly specked with cinnamon brown and marked evenly 

 with faint lavender, to an egg which has a grf>und color twice as deep as the 

 egg .iust mentioned, and heavily splotched with dark olive and dark lavender. 

 There is also one set of three which is especially unlike the others, in tliat the 



