294 THE NESTS AND EGGS OF BRITISH BIRDS. 



or thrift, made of turf, branches of heather, leaves and 

 stalks of marine vegetation, and sea-weed, and lined with 

 grass, much of it semi-green. The poorer nests are 

 usually made in hollows of the downs, or in ledges of 

 crags, or amongst broken rock, and these are mere 

 depressions more or less sparingly lined with grass and 

 perhaps one or two feathers. When the colony is 

 invaded by man the birds rise in crowds from their nests 

 and circle overhead, uttering their incessant cries. Few 

 sights are grander than the colony of these birds at the 

 Fame Islands, the gulls filling the air literally like a 

 heavy snowstorm. 



Range of egg colouration and measurement : 

 The eggs of the Lesser Black-backed Gull are usually 

 three in number, but sometimes four. They vary in 

 colour to an astonishing degree. I made the following 

 note on their colour from a heap of many thousands : 

 pale green, bluish-white, dark olive-brown, pale brown, 

 buff, and gray constitute the ground colours, and the 

 spots and blotches vary from dark liver-brown to pale 

 brown and gray. Some eggs are streaked almost like 

 those of a Bunting, others are finely marked over the 

 entire surface ; whilst others yet again are boldly 

 blotched, or have most of the markings in a zone round 

 the larger end. Average measurement, 2"j inches in 

 length, by rp inch in breadth. Incubation, performed 

 by both sexes, lasts about a month. 



Diagnostic characters: Unfortunately I know of 

 no absolutely reliable character by which the eggs of 

 this Gull can be distinguished from those of the Herring 

 Gull, or from certain varieties of those of the Common 

 Gull. Those of the former species, however, are gener- 

 ally larger, those of the latter smaller, whilst on both the 

 markings generally take the form of spots rather than 

 blotches. Careful identification, however, is necessary. 



