BRITAIN'S BIRDS AND THEIR NESTS. 47 



are laid with nothing between them and the hot sand ; 

 but more usually there is some attempt at lining the 

 scraped-out hollow, bent-grass or herbage of some sort 

 being generally used. The nests are not always placed 

 on sand, of coiu'se ; but whether difference of situation has 

 any effect on the type of nest is doubtful. It is some- 

 times said that the amount of lining depends on the 

 dampness of the ground ; but we have noted dozens of 

 cases where a perfectly unlined ' scrape "* and a com- 

 paratively bulky nest lay within a yard of each other, 

 both on dry sand. 



Incubation lasts about three weeks, and the young 

 leave the nest at once and begin to wander about the 

 colony, showing considerable aptness in concealing them- 

 selves in the tufts of bent-grass at the approach of 

 danger. It is certain that even in these large colonies 

 Gulls and Terns know their own nests infallibly ; but 

 whether they can distinguish their own offspring from 

 among the hundreds of chicks is more doubtful. The 

 down plumage is very similar to that of the Black-headed 

 and other Gulls. 



When the young have attained full size and the power 

 of flight, they journey with their parents to the shore, 

 if they are not already practically there. Here they 

 remain for several weeks more — till late in September in 

 some seasons — before migrating to ' coasts that keep the 

 sun."" On the shore they still remain markedly gregarious, 

 and old and young keep together in large flocks, 

 spending most of their time standing or sitting on the 

 sandbanks. Some of the old birds, however, are usually 

 away fishing, and their method of doing this is interest- 

 ing. Like Gulls, they quarter the water methodically, but 

 with less regularity and at a greater height above the 

 surface. The prey once marked, the descent is a head- 



