LIFE HISTORIES OF NORTH AMERICAN GULLS AND TERNS. 283 



over the rest of the egg. A very handsome type has the brown laid over the 

 vinaeeous, and occasionally the deep burnt sienna or chestnut shading off to 

 one side into light, caused by the spiral twisting of the egg in the oviduct. 

 One .specimen shows this to a marked degree, having long chestnut daubs 

 extending spirally from the big end. Still another type has fine brown and 

 grayish vinaeeous maculations scattered all over the egg, but more numerous 

 at the blunt end. An abnormal specimen is entirely without markings, being 

 pure white. The shai^ is ovate, either elongate or thick. An average specimen 

 measures 53 mm. by 35 mm. 



The measurements of 76 eggs, in the United States National 

 Museum collection, average 50 by 35 millimeters; the eggs showing 

 the four extremes measure 56 by 36, 54,5 by 37.5, 44.5 by 35 and 48.5 

 by 33 millimeters. 



Young. — Both sexes incubate, and, according to Prof. Watson's 

 observations, the shift is made during the night, each bird remaining 

 on the nest 24 hours except for occasional short excursions for water. 

 The incubating bird is evidently fed hj its mate. Based on the 

 study of 16 nests he determined that the period of incubation is 26 

 days. During the first three days after the young are hatched they 

 are closely guarded by their parents, after which they learn to " run 

 to the bushes, where they remain motionless after sticking their heads 

 into the crotch of some bush or depressing the body against any 

 convenient solid object." The parents soon learn to recognize their 

 own young, and the young learn to respond to the calls of the parents. 

 Each bird feeds it own young and attacks the young of anj'^ other 

 bird which invades its territory. This leads to many fights among 

 the adults and much mortality among the young. Professor Watson 

 (1908) says: 



The parents alternately feed the young, but instead of a diurnal period of 

 feeding, sucli as tlie parents have before the appearance of the young, the inter- 

 vals vary anywhere from four to seven hours. My observations are few on 

 this point. Though the parents feed the young at any hour of the day, feeding 

 can be most easily observed at dusk. It has already been mentioned that the 

 sooties hurry home at nightfall in great numbers. From 4 until 8 p. m. this 

 feeding process keeps the island in commotion. The feeding of the young birds 

 has many interested spectators. While I have never seen the terns from the 

 neighboring nests, which may be observing the process, attempt to rob the 

 young bird, I judge from the actions of the feeding parent that such is occa- 

 sionally the case. If the parent happens to disgorge more than the young tern 

 can take into its beak, and the food is allowed to fall to the ground, it is 

 ludicrous to watch the rapidity with which the parent picks up the food and 

 reswallows it. Often times the mate of the feeding parent is near; its rSle 

 is a purely passive one, except when the " spectators " attempt to approach 

 too near. Its part is then to assist in warding them off. 



The care of the young, especially from 20 days on, must be an exhausting 

 process for the parents. They become emaciated and .somewhat bedraggled in 

 appearance. This is not to be wondered at when we consider that a healthy 

 young sooty can eat anywhere from 20 to 40 minnows of no insignificant size 



