INTRODUCTION. 29 
and mode of life. The common species is very often to be seen 
on the banks of the Thames, and many of the Gulls, though 
familiar objects at the sea-side, largely frequent inland waters, 
feeding on worms, insects, eggs, the nestlings of other Birds, 
mice, &c., as well as fish. Their flight is graceful, and they 
may often be seen sailing in circles in the breeze, with hardly a 
perceptible motion of the wing. 
The Terns are yet more graceful in flight, but they walk 

The Common Gull (Larus canus). 
with less ease, though they swim admirably. Their more slender, 
less bulky aspect, straighter bills, narrower wings, and long 
forked tails serve, with few exceptions, to distinguish them from 
the Gulls. There are, again, some fifty species of this group, 
some or other of which are to be found nearly all over the 
globe. Like the Gulls, they are noisy and gregarious, and 
are found on inland lakes as well as the sea-shore, feeding on 
insects as well as fish. The Arctic Tern (Sterna macrura, fig. 28) 
may serve for a type, as it is almost as well known as the 
so-called Common Tern (S. fluviatilis). It comes to us in the 
latter half of April, breeding on islands near the coast. 
