COMMON TERN AND BLACK-HEADED GULL. 141 



shank's nest. The grass surrounding their nests always became 

 discoloured and withered, as sitting progressed, from contact 

 with the bird. Although there were a few nests with absolutely 

 no lining, the eggs being laid and incubated and hatched in a 

 slight depression of the ground and grass, the rule was a sub- 

 stantial pad of fine grass, plucked green, but drying afterwards, 

 with an occasional substratum of purslane stems and thrift 

 stems. Exceptionally, purslane leaves were added on the top. 

 I took the material out of many of the nests after they were 

 hatched off, and it generally made a big double handful of dry 

 vegetable matter. This lining was accumulated gradually by 

 the sitting bird. In the majority of cases my notes record a 

 " slight " lining on the first finding of the nest ; and a " thick " 

 lining, or a "big pad," on the visit a week later. This was 

 particularly noticeable after one wet week, when I found a 

 number of nests made up with fresh material on the top of 

 the old. 



The Gulls chose spots for nesting as a rule amongst rather 

 long vegetation, either grass or purslane, which would admit of 

 a good-sized hollow being formed, in which the usual bulky nest 

 of stick and straw foundation could be built, finished off by a 

 well-formed cup, lined with finer materials. A variant on this 

 type was often built on bare ground, the foundation of bulky 

 material raising the cup several inches off the ground. The 

 building of the Gulls' nests seemed to be completed before the 

 first egg was laid. 



The nests of both species were used after the eggs were 

 hatched, either by the nestlings squatting in them, or possibly 

 by the parent bird brooding over its young, the nests becoming 

 spattered all round with limy excrement. The Gulls' nests 

 had also distinct " pads " over their margins where the young 

 birds had been going in and out. In several instances there 

 were two of these pads to a nest, and then always opposite 

 each other. 



There were a few abnormally coloured Tern's eggs in the 

 colony. In one clutch of two the ground colour was a pale 

 green with olive markings. The bird to which these eggs 

 belonged had lined its nest with fresh green purslane leaves, 

 and the green ground colour of the eggs corresponded exactly in 



