138 ODD HOURS WITH NATURE 



scheme of their colouration is a very ancient 

 adaptation, for it is common to the whole group 

 of sea-birds of which it is a highly specialized 

 member. A description of the tern's egg, as regards 

 everything but size, would apply to the eggs of the 

 kittiwake, common gull, lesser black -backed gull, 

 and the black -headed gull ; and such a community 

 of colouring points to the scheme being an adapta- 

 tion to the breeding conditions of the common 

 ancestor. But to-day each species selects a 

 different kind of nesting -place, and in the case 

 of some of them the protection of colour is 

 obviously not even sought. The kittiwake depends 

 upon the security of its rock shelf, and the black - 

 headed gull on the isolation of its swampy 

 islands ; perhaps, too, on the strength of its com- 

 munities, which is always sufficient to keep thieving 

 birds at a distance. Of the common gull some- 

 thing of the same might be said. Since inspecting 

 the " ternery," the writer has visited a colony of 

 the common gull (not, by the way, the commonest 

 of gulls by any means), which has its home on the 

 rock -strewn shore of one of the largest of the 

 inland Highland lochs. The eggs are in perfect 

 harmony with the mossy blocks among which they 

 lie, but all the advantage of elusive colouring 

 is thrown away by the structure of the nests, 

 which are in every case large and conspicuously 

 made of pale yellow, bleached grass -stalks and 

 kindred dead vegetation. Apparently in some 

 members of the family the protective colouration 

 of the eggs is a functionless survival of an 

 acquisition which may have been advantageous at 

 some remote time. 



