this “tribe” are the gulls and terns. The peculiarly graceful, 
elastic flight of these birds surely needs no description. Even 
town-dwellers know them well. For during the winter months 
they follow the rivers far inland. Even in grimy London they 
may be seen in hundreds during the winter months. The black- 
headed gull is by far the commonest of these winter visitors. But 
at the same time, to the uninitiated, the name “‘ black-headed ” 
must seem singularly inappropriate ; for its head is emphatically 
white. At no time, indeed, is it ever black. But keep careful 
watch of the hosts which throng the river from January, onward,, 
till they depart for their breeding quarters, and you will see them 
gradually developing a dark patch on each side of the head. And 
this slowly spreads till the whole head is of a dark sooty brown. 
Immature birds may be picked out by the presence of brown 
feathers in the wings, and a black bar across the tip of the tail. 
Here and there among them, one may see much larger birds of a 
brownish grey colour, and with black beaks and pale coloured 
legs, in place of the cherry-red of the beak and legs of the ‘‘ black- 
headed ” species. These are the immature stages of the greater, 
and lesser black-backed gulls; or of the herring gull. When 
fully adult the two first-named have the back and wings of a dark 
slate colour, the rest of the plumage dazzling white. The beak 
is pale yellow, with a red spot on the angle of the lower 
jaw. During flight the wings are also black, but the 
