LIFE HISTORIES OF NORTH AMERICAN GULLS AND TERNS. 39 



meters ; the eggs showing the four extremes measure 62.5 by 42.5, 58 

 by 43.5, 53 by 39 and 55 by 37.5 millimeters. 



Young. — The period of incubation is said to be 26 da3^s. Probably 

 both sexes incubate, as both parents are usually together at the nest 

 and both are devoted to the young. The young remain in the nest, 

 where they are fed by their parents, until they are fully fledged. 

 The narrow confines of the usual nest, on its small shelf of rock, per- 

 mit no wandering habits, as common among other gulls. Any 

 attempt to stray from the nest would usually result in a disastrous 

 fall from a dizzy height to dangerous rocks or surf below; so the 

 young birds must of necessity stay in the nest until able to fly. 

 Many such fatal accidents probably occur, which serve to keep in 

 check the increase of the species, which is otherwise secure from 

 molestation on its nesting grounds. 



On North Bird Rock, where many of the nests are on the lower 

 ledges, I noticed on July 24, 1915, that many of the nearly fledged 

 young had been able to crawl or jump out of the nests and were 

 wandering about over the flat rocks below the cliffs, though they 

 were not able to fly. Many of the older young were already on the 

 wing at this date and a few were still in the nests. 



Plumages. — The newly hatched young is covered with long, soft, 

 glossy down, which is white and spotless, but tinged basally with 

 yellowish gray and buffy on the back and thighs, and tipped with 

 dusky, giving it a grizzly appearance, quite unlike other young gulls. 

 The young bird grows rapidly and soon begins to assume the first 

 winter plumage, which appears first on the scapulars, then on the 

 wings, back, and neck. There is no strictly juvenal plumage in this 

 species. In the first winter plumage the bill is black; there is a 

 blackish patch on the hind neck; the lesser wing-coverts and some- 

 times the greater wing-coverts and scapulars are largely black; the 

 tail has a broad black band at the tip ; the duslcy spots on the head, 

 before and beliind the eye, are darker than in adults. A partial 

 molt occurs early in the spring, usually in February and March, 

 but sometimes as early as December, in which most of the dusky 

 feathers in the head are replaced by white or lighter colored feathers 

 and the black lesser wing-coverts disappear. At the first postnuptial 

 molt in August young birds become indistinguishable from adults 

 when one year old, a complete molt producing the adult Avinter 

 plumage. A partial prenuptial molt, involving the head, neck, and 

 body feathers, produces the adult nuptial plumage with the pure 

 white head and yellow bill. Adults have a complete molt in the 

 summer, producing the well-lmown winter plumage. 



Food. — A flock of feeding kittiwakes is an animated and a pretty 

 sight. During the latter part of the summer they assemble in enor- 

 mous numbers in the numerous bays and " tickles " of the Labrador 

 1747S.5— 21 1 



