BIRDS 425 



avoid treading on them. The birds which are bred in the 

 neighbourhood of water, and which swim strongly at an early- 

 age (though they do not like to cross a lough in the teeth of a 

 strong wind), rarely attempt to escape capture by swimming. 

 If danger threatens they usually run in for shelter to the bank ; 

 there, if you search, you are sure to find the fugitives stowed 

 snugly away in the sedge or rushes. But as the young begin 

 to feather they skulk less, and draw together in level places 

 among the sandhills or under lee of some island that offers a 

 screen from the wind. The social instinct, thus early mani- 

 fested, becomes even more obvious when the birds feather and 

 can take short flights. Some youngsters are very independent, 

 and prefer to cruise about by themselves, others follow their 

 parents with amusing perseverance, but the greater number 

 congregate together in parties of twenty and thirty birds, 

 until, their pinions growing strong, they leave the nursery on 

 their own account or accompany their parents to fresh waters 

 in search of food. 



For the first few weeks of their feathered existence the 

 young birds are conspicuous, owing to the dark colour of the 

 nest plumage, but when the grey mantle has been assumed, in 

 September, the old birds and juveniles are not very dissimilar, 

 though of course the black bar across the tail, and wing coverts 

 mottled with brown, tell their own story. It is very unusual to 

 see any birds of the year at a breeding colony, so unusual that I 

 have only one note of having observed a Black-headed Gull, 

 possessing a black bar, upon the tail, associating with nesting 

 birds, i.e. at Moorthwaite in 1889. 



Individuals show considerable variation in the time at which 

 the dark hood is donned. In the year 1889 I came across an 

 example which showed no sign of assuming a black head on the 

 20th of May. An interesting topic, and one deserving wider 

 attention than it appears to have received hitherto, is that of 

 the epidemics which occasionally attack whole colonies of birds in 

 the breeding-time. The Black-headed Gull is a typical sufferer. 

 In certain years the percentage of deaths among the unfledged 

 birds is so high at Ravenglass that wherever you go in the 

 midst of the gullery you find the bodies of the birds in all 



