240 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



two weeks in June and plenty of fresh eggs may be found up to the 

 Fourth of July. Formerly, when much disturbed, egg laying was 

 prolonged through August, but now only a few belated sets are to be 

 found in that month. One egg is laid each day until the set is com- 

 plete, which normally consists of three eggs, often four, sometimes 

 five, and very rarely six. Frequently, sets of four, and usually the 

 larger sets, show evidence of having been laid by two birds, either 

 by marked difference in color, shape, or size, or by different degrees 

 of incubation. Many eggs are dropped indiscriminately anywhere, 

 probably by birds unable to reach their nests in time, and left to 

 bleach in the sun. Such eggs are often broken, as if dropped by 

 birds in the air. 



On the islands near Penobscot Bay, Maine, which are mostly 

 high and roclcy or covered with grass, I have examined a number of 

 small breeding colonies of common terns. The nests were on the 

 higher portions of the islands in open situations, either on bare 

 rocky or stony ground or in the short grass, frequently near or even 

 on pieces of driftwood or bunches of seaweed. They were merely 

 slight hollows in the ground, carelessly lined with bits of straw, 

 grass, or rubbish. Once I saw a broken sea-urchin's shell half in- 

 closing one of the eggs. There are numerous small and several large 

 breeding colonies scattered along the New England coast where the 

 terns adapt their nest building to the conditions existing. These are 

 almost invariably on islands, and generally on small islands, which 

 are inaccessible to predatory animals. Notable among these are 

 Penikese and Weepecket Islands, south of Buzzards Bay, Mas- 

 sachusetts, where both the common and roseate terns breed in large 

 numbers, nesting among the stones and rocks on the beaches or on 

 the grassy uplands. Occasionally a nest is found lined with small 

 stones, as if collected for that purpose. On Cobb's Island, Virginia, 

 and on the adjacent islands, we found a few small colonies of com- 

 mon terns, nesting on the beaches with the gull-billed terns and 

 black skimmers, and on drift seaweed in the marshes. Mr. B. S. 

 Bowdish (1910) mentions a colony of 250 common terns breeding on 

 Royal Shoals, a low sand spit on the coast of North Carolina, to- 

 gether with least terns, black skimmers, and laughing gulls. The 

 most southern breeding colony I have ever seen was in the Breton 

 Island reservation off the coast of Louisiana, a small colony of about 

 25 pairs on Battledore Island scattered among the large breeding 

 colonies of laughing gulls and black skimmers. 



In Lake Winnipegosis we found a number of large colonies, on 

 small rocky or stony islands, breeding in company with ring-billed 

 gulls, double-crested cormorants, and white pelicans. Some of these 

 colonies contained over 1,000 pairs of terns, nesting in dense groups 



