PLOVERS, GULLS, AND AUKS 83 



part of the neck become slightly flecked with grey. In the Kitti- 

 wake the hind-toe has become reduced to the vanishing-point. 



The Black-headed Gull (Plate XVI. fig. 4) differs from those 

 just described in that during the summer months the feathers of 

 the head develop a dark brown colour, which, when the bird is flying, 

 gives the head the appearance of black, hence its name. Young 

 birds in their first plumage may be readily distinguished by the fact 

 that the smaller feathers of the wings are brown in colour, while the 

 tail has a black bar across its tip. But the completely adult characters 

 are assumed on the completion of its first year, and in this it 

 contrasts strongly with the Herring- and Black-backed Gulls, which 

 require years wherein to perfect their plumage. 



During the winter months the Black-headed Gull has, for some 

 years past, assembled in large numbers on the Thames, as far up 

 as Kew, and on the ornamental waters of the London parks, adding 

 greatly to the interest of life in London to those who, having a love 

 for Natural History, are perforce compelled to live in town. 



The small, fork-tailed, short-legged birds known as Terns are 

 really very closely related to the Gulls, but they have relatively 

 longer wings and a more graceful flight and fashion of procuring 

 their food. 



The species known as the Common Tern (Plate XVL fig. 8) is 

 the most abundant representative of the Tern tribe in Great Britain 

 and Ireland, coming to us in the month of April and departing in 

 the autumn. It also breeds abundantly in North America, from 

 Labrador to Texas, though scarcely known on the Pacific Coast. 



In some parts of England this bird is known as the '* Gull-teaser," 

 from its habit of chasing Gulls and compelling them to drop the fish 

 they have just captured. This done, by a swift plunge the ill-gotten 

 prize is seized before it reaches the water. But in catching prey in 

 a more legitimate way it displays considerable skill, feeding upon 

 young coal-fish and sand-eels, shrimps, and other crustaceans. 



The eggs of this bird, like those of the Terns and Gulls generally, 

 bear a close resemblance to their surroundings, and hence are said 

 to be protectively coloured. And this is no less true of the downy 

 nestlings. When full grown the Common Tern measures about 14 

 inches in length, but of this some 6^ inches is made up by the long 



