250 THE BIRDS OF THE BRITISH ISLES. 



when it sights food on or near the surface ; sometimes its descents 

 and ascents are long, graceful swinging curves, varied with a 

 check and flutter as it intercepts some dodging fly or gnat, but 

 often it dives obliquely with a half turn, lightly touches the 

 water with its bill, leaving a circle of ripples where an insect 

 swam or drowned, and banks smartly. Its loitering flight is 

 broken by a series of deep U-curves. But rarely it strikes the 

 water with its body, and I have only once seen a bird submerge. 

 Like the Swallow it feeds against the wind, sweeping down 

 wind to repeat the process when it reaches the limits of the 

 pool. When tired it settles on some rail or mooring-post ; on 

 this it perches head to wind, its head and neck depressed, its 

 long wing tips crossed above its short tail and s-lightly raised ; 

 it tilts forward in its resting position. It is sociable rather 

 than gregarious on migration, often flying with Common and 

 Lesser Terns, when its even more buoyant flight is very marked. 

 Large numbers have, on rare occasions, been recorded from 

 the east coast, but more than fifty in a party is unusual; in 

 Cheshire, twelve and twenty-four are the two largest flocks 

 observed. 



The Marsh Terns, as the members of this small group are 

 called, are inland rather than sea terns, more frequent over 

 fresh than salt water ; even when travelling along the coast of 

 Lancashire they keep to the dunes, feeding over the " slacks," 

 rather than the shore. They seldom swim, the webs being 

 more deeply indented between the toes than in other terns, 

 the feet better fitted for walking. The Black Tern nests in 

 extensive and treacherous marshes, the nest itself (Plate 113), 

 built of sodden and often rotten vegetation, is frequently 

 surrounded by water, placed on a quaking platform of dead 

 aquatic plants. The bird is demonstrative at the nesting 

 colony ; Pennant, writing at the beginning of the nineteenth 

 century, says — "They are found during spring and summer in 

 vast numbers in the fens of Lincolnshire; make an incessant 



