THE GULLS 24I 



solicitously. She also adopts the typical begging-for-food position, 

 described for the other gulls. 



Gulls build nests from materials near at hand: of seaweed, grass, 

 maritime plants, heather, lichen, etc. Bonaparte's gull [Larus Phila- 

 delphia)^ and occasionally the black-headed gull, nest in trees. The 

 great black-backed gull will decorate its nest with the remains of the 

 carcases of its victims: shearwaters, puffins and auks. The black- 

 headed gull uses rushes, sedges and small sticks; but individuals 

 may make little or no nest, laying their eggs in a scrape in the ground. 

 Kittiwakes form collecting parties, like gannets, and tear grass and 

 herbage from the sides of cliffs ; they cement the nest together in its 

 precarious situation by much treading with the feet, and they have been 

 observed to carry mud-like material in their bills. Both sexes assist 

 in nest construction; the male of the black-headed gull takes the 

 initiative, doing much of the construction with material supplied 

 by the female, but in some species the amount of nest building by 

 each sex has not been fully ascertained owing to the difficulty of 

 identifying the sexes in the field. 



The eggs of gulls are usually three in a clutch, and vaiy consider- 

 ably in the shade of the brown, olive or greenish-blue ground colour, 

 but all are spotted or blotched with darker brown or black. Although 

 this colouring is protective and renders them inconspicuous at a 

 distance, this advantage is somewhat lost by the conspicuous appearance 

 of the head (white or dark brown) and white breast of the sitting adult; 

 and also by the fact that when a large breeding colony of gulls is 

 disturbed by man or other large mammal, the occupants rise in a 

 screaming mass overhead, advertising the position and extent of the 

 colony. This action does, however, divert attention from individual 

 nests which are then partly protected by the drab camouflage colour 

 of the eggs or chicks. However, as we have seen, unless disturbed by 

 human beings or other formidable enemies, one or other of the pair 

 remains at the nest, once the eggs are laid; and incubation may or 

 may not begin with the laying of the first tgg. There is an interval, 

 among the larger gulls, of at least one day between the laying of each 

 tgg. Incubation is by both sexes, but apparently the female takes the 

 greater share. As will be seen in the following table, the period varies 

 between twenty and twenty-eight days. 



There is often severe loss of eggs and chicks occasioned through 

 egg-collecting (for food) by humans, and raiding by dogs, foxes, 

 otters, stoats, etc. Individual gulls, members of the colony, indulge 



R 



