214 THE BIRDS OF THE BRITISH ISLES. 



The hoarse, barking airji, agh, agh, differs from the notes 

 of other gulls, and when I have been at the nest, the old bird 

 wheeled high overhead with deep guttural, angry barks, ugh, 

 7igh, more emphatic than the normal note. The challenge, 

 however, uttered with head raised, differs but little from that 

 of its congeners. After this vociferous call, the bird lowers the 

 head below the level of the raised shoulders, and peers from 

 side to side as if expecting a reply. All gulls are omnivorous, 

 but the Great Black-back prefers its meals to be of flesh, either 

 recent or ancient. A dead rat, dog, or whale is alike accept- 

 able to the " Corpse-eater " ; where the carcase is there will 

 the Black-backs gather, keeping the smaller fry away. It will 

 pounce upon and half devour the " cripple," before the wild- 

 fowler can gather it ; it ruthlessly slays its neighbours, the 

 Puffins and Shearwaters, tearing out their entrails and leaving 

 the rest for the rats ; it has been known to bolt whole so large 

 birds as Redshank and Little Auk. Mr. J. A. Dockray saw one 

 chase and capture on the wmg a passerine bird which was 

 crossing the Dee estuary. I have not seen the Great Black- 

 back drop molluscs, but it has been known to lift and drop 

 the Puffin which it had been worrying, after shaking it as a 

 dog shakes a rat. 



In England and Wales this bird usually nests singly on the 

 top of some stack or rocky headland, but in Ireland and 

 Scotland there are some large colonies. It occasionally nests 

 in the centre of a colony of Lesser Black-backs. On Puffin 

 Island, though no Great Black-back was visible, Miss E. L. 

 Turner and I examined a nest which contained three eggs, two 

 of them typical eggs of the Lesser Black-back, and one which 

 measured 76 by 58 mm., about the size of the Qgg of the Greater 

 Black-back. It was long doubted if the bird nested in the Isle 

 of Man ; Mr. T. Taylor, however, found and photographed the 

 nest shown on Plate 97. The nest is an untidy collection of 

 seaweed, thrift and grass torn up by the roots, sticks, and 



