LIFE HISTORIES OF NORTH AMERICAN GTJLLS AND TERNS. 167 



The nests were all built of the same material — old water-soaked bullrushes — 

 with sometimes a few fresh stems worked into the upper part, A heavy 

 foundation of the thickest and longest rushes is first laid, forming a partly 

 submerged platform held in place by the standing rushes about it, the whole 

 being 2 to 3 feet across at the water line. Upon this the rather well- 

 made superstructure of finer material is constructed, with a long slope from 

 the water's edge up to the rim of the nest, which is raised 8 inches to a 

 foot above the water. The cavity is 8 to ,10 inches in diameter and 3 to 4 

 in depth, and is rudely lined with bits of fine rush tops and coarse grass. The 

 inside is always perfectly dry, being several inches above the water. The 

 variation in the nests was not very gi'eat, being merely as to general bulk 

 and height. Much of the material of which the nests were constructed had 

 been carried from a distance, probably from the neighboring shore, where 

 the rushes, loosened by the ice, had been cast up in heaps. The gulls carry 

 with apparent ease these great heavy rushes, and were often to be seen 

 flying about for a considerable time with the long stems dangling from their 

 bills. The nests were kept in good repair, and as they became trampled down 

 or the rim disarranged the owners were to be seen putting things to rights 

 or adding a new rush here and there as it was needed. At the time of our visit 

 many young were already out of the shell, but there were also many sets of 

 eggs in all stages of incubation, the result probably of second nest building. 



Eggs. — As with most gulls the normal set of eggs is three ; sets of 

 four are rare, and often such sets are apparently the product of two 

 birds; two eggs sometimes constitute a full set. The eggs show an 

 interesting series of variations. In shape they are usually ovate, with 

 some variation toward elliptical ovate. The shell is thin and almost 

 lusterless. The ground color shows a great variety of buffy and 

 greenish buffy shades, from " buffy brown " or " deep olive buff " to 

 " cream buff," and from " ecru olive " or " water green " to " vetiver 

 green " or " pale olive buff." Some eggs are sparingly spotted and 

 others are quite heavily marked with large and small spots, blotches, 

 or irregular scrawls, which sometimes are confluent into rings, of 

 various shades of broAvn, such as " seal brown," " sepia," " bister," 

 " Vandyke brown," and " burnt umber." Some eggs have a few 

 spots of " lilac gray." The measurements of 48 eggs, in the United 

 States National Museum collection, average 52 by 36 millimeters; 

 the eggs showing the four extremes measure 56.5 by 37, 53.5 b}'^ 38.5, 

 47.5 by 35.5 and 49.5 by 34 millimeters. 



Yomig. — I am inclined to think that both sexes incubate, for they 

 are apparently affectionate and devoted to each other, both birds 

 being often seen standing side by side on the nest. I believe that the 

 male stands beside his sitting mate much of the time and relieves her 

 by taking his turn on the nest. Dr. Roberts (1900) says that the 

 period of incubation is "probably 18 or 20 days." He gives the 

 following interesting account of the behavior of the young: 



These pink-footed, pale-billed little balls of down now and then remain 

 quietly in the home nest, basking in the warm sunshine, but more frequently 

 they are no sooner dry from the egg than they start to wander. A few are 

 174785—21 12 



