292 THE NESTS AND EGGS OF BRITISH BIRDS. 



particular spot. The nest is generally made on a stack 

 of rocks, or a ledge of the cliffs ; less frequently on the 

 ground, on an island. It is slight and loosely put 

 together, a mere hollow in most cases, carelessly lined 

 with grass, twigs, dry sea-weed, or stalks of marine 

 vegetation. I have known the eggs to be laid on the 

 bare ground, in a hollow amongst the crags. The birds 

 sit lightly, but are bold and clamorous when disturbed 

 from the nest. 



RANGE OF EGG COLOURATION AND MEASUREMENT : 

 The eggs of the Great Black-backed Gull are usually 

 three in number, less frequently two, and rarely even one. 

 They vary from grayish-brown to brown tinged with 

 olive in ground colour, spotted with dark umber-brown, 

 and with underlying markings of brownish-gray. As a 

 rule the markings are not very numerous, range in size 

 from that of a buckshot downwards to a speck, and are 

 distributed over most of the surface. Some varieties, 

 however, are most heavily marked on the larger end. 

 Average measurement, 3*1 inches in length, by 2'i inches 

 in breadth. Incubation, performed by both sexes, lasts 

 about a month. 



DIAGNOSTIC CHARACTERS : The large size and small 

 markings readily distinguish the eggs of this Gull from 

 those of allied species breeding in our islands. 



