250 SEA-BIRDS 



calling querulously for food, and an adult which happens to have its 

 crop full of food may respond to the persistent begging of a juvenile, 

 not necessarily its own child. The young gulls, like many other juvenile 

 sea-birds, drift away from the breeding ground on their migration 

 route, independent of the adults. The lesser black-backs travel farthest 

 — as far south as the Iberian peninsula and North Africa. Many of 

 these migrants remain in waters about the southern limit of their 

 winter range until full adult plumage is acquired during their fourth 

 year. They may be seen about the harbours of Portugal and the Bay 

 of Biscay. Few return to their breeding grounds with incomplete 

 adult plumage. But the juveniles of glaucous, great black-backs and 

 herring-gulls do not travel far from their breeding coasts, although there 

 is a general local southward trend; the majority remain within a few 

 hundred miles of their birth-place. The adults are even more sedentary 

 than the juveniles. During adolescence gulls of sedentary species will 

 frequent harbours and estuaries the whole year round, but a few of 

 the older ones, whose plumage is nearly mature, may visit in summer 

 those breeding grounds which lie within easy flight of these feeding 

 grounds. 



The complete moult takes place in autumn, and a second moult, 

 of the body feathers only, occurs early in the spring, when the streaky 

 winter appearance of the adult head and neck is replaced by pure 

 white, or, in the brown-headed species, by the t}^ical dark hood. 

 The smaller gulls, e.g. the black-headed, common and kittiwake 

 species, acquire the mature plumage after their second winter, one 

 or two years in advance of the large Larus gulls. 



