Vol.X 



" s ' 1 Mackay on the Breeding Habits of Larus atricilla. ??c 



being placed on one of the higher sand ridges or hummucks, 

 with which the marsh was interspersed, and which were covered 

 with high grass. A few pairs (three or four) nested very near 

 this same place in June 1S93, but the larger number I found to 

 be nesting about fifty yards further inland from the spot where 

 they bred in 1S92. This nesting place was in a depression or 

 basin where the beach peas were growing in profusion, and here 

 I found nine nests (all the eggs in which were partially incu- 

 bated), all of which were composed entirely of beach grass 

 stubs'about five or six inches long, interwoven and placed on top 

 of a cluster of dead stubs of the same material the tops of which 

 had disappeared, which raised the nest some five or six inches 

 from the sand. There was little attempt made at concealment, 

 that little being furnished by the higher growth of the beach peas 

 which surrounded them. These two places were the only ones 

 on the island where I discovered their nests, or noticed that thev 

 congregated and I much doubt if there are any others in this 

 locality. Of the nine nests discovered each contained three eggs 

 except two which had two only. On June 22, 1S93, four or five 

 more nests were discovered by some of my friends not far from 

 where I found mine, all of which contained three eggs each. I 

 was on the island of Muskeget July 3 and 4, 1S93, but saw no 

 young. While I am not certain how r many eo'gs constitute a 

 complete set, I am of the opinion that the number is three. 



During the summer of 1890 four nests were found on July 10, 

 each of which had five eggs, and in [891 and 1S92 other nests 

 were found which also had five eggs in each, all the other nests 

 discovered in these years having two or three eggs each. It is 

 possible more than one female may have deposited eggs in the 

 same nest. The eggs are nearly if not quite three times .is large 

 as those of Sterna hirituJo, which some of them somewhat 

 resemble, though darker in color, being as large as a pullet's egg. 

 Their ground color is pale olivaceous, with a slight tinge of 

 brown which last in some eggs shows stronger than in others. 

 In some sets this ground color assumes a muddy appearance, 

 while in others it is quite clear. The entire egg is covered over 

 with dark chocolate-colored irregular marks and spots, which in 

 some eggs run one into the other at the larger end, making it the 

 most prominently chocolate-marked portion of the egg. 



