GULLS 101 



is, therefore, coloured to conceal it on the rocks 

 and shore, where it awaits the return of the 

 fishing gull. 



I have watched the lesser black-back and 

 common gull feed upon my observation ponds, 

 and from the behaviour of the fish I am certain 

 that it does not detect the presence of the 

 surface-swimming gull until the bird is almost 

 over it — that is, within the fish's " window." 



The lower photograph on the accompanying 

 plate shows a lesser black-back plunging under 

 the water after a fish. The gull was right over 

 its prey before the little fish darted directly 

 downwards. 



Though, speaking generally, I consider the 

 black and white plumage of gulls as a scheme of 

 aggressive concealment, the same arrangement 

 of plumage undoubtedly protects them from 

 enemies below the water. 



Reference has already been made to the fact 

 that when an enemy approaches from below, its 

 " window " narrows down so that a flock of gulls 

 on the surface slip into the area of total reflec- 

 tion, and only the bird for which the predatory 

 beast or fish is making remains as a dark 

 silhouette against the sky. 



