256 BRITISH BIRDS. 



placed in somewhat scattered colonies^ and each nest is a substantial 

 structure of rotten reeds^ dead horsetails, or decaying pond-weed or 

 other water-plant. Three is a full clutch of eggs. They vary in 

 ground-colour from greyish buff to huffish brown, and are thickly spotted 

 and blotched with rich reddish brown and very dark blackish brown, 

 with underlying markings of greyish brown and inky grey. Few eggs 

 are more boldly marked than those of the Black Tern. On most of 

 the eggs the large blotches are confluent, often forming broad irregular 

 bands round the broadest part of the shell or round the large end. 

 Some eggs have the markings smaller and more evenly distributed over the 

 surface. The underlying spots are often large and generally conspicuous. 

 The eggs vary in length from 1'46 to 1'3 inch, and in breadth from r05 

 to '9 inch. It is impossible to give any characters by which the eggs of 

 the Black Tern can be distinguished from those of the White-winged Black 

 Tern ; but those of the Whiskered Tern can readily be distinguished by 

 their larger size, and on an average paler and greener ground-colour and 

 smaller markings. Although the eggs of the Whiskered Tern overlap in 

 measurements those of the Black Tern, they are constantly larger in bulk. 



The Black Tern feeds principally on insects, worms, water-beetles, and 

 aquatic larvse of all kinds ; it also catches dragon-flies and other insects 

 on the wing, and occasionally drops down on a fish or a tadpole. In its 

 winter-quarters it frequents marshes and lakes in small parties ; and my 

 friend Mr. Labouchere has seen the American form of this species follow- 

 ing the plough on the jirairie farms of Minnesota to feed on the worms and 

 grubs. 



The Black Tern is the smallest British Tern, except the Lesser Tern. It 

 has long wings, but the tail has not a deep fork (about | in.). The adult 

 m summer plumage has the entire head, neck, breast, and belly sooty 

 black ; the vent and the under tail-coverts are white, and the rest of the 

 plumage is slate-grey, much paler on the under wing-coverts. Bill black; 

 legs and feet reddish brown ; irides dark hazel. After the autumn moult 

 the forehead, lores, chin, and throat become white, and the breast and belly 

 are barred with white. 



After the first spring moult the young bird differs from the adult in 

 having nearly black lesser wing-coverts, and in having the belly barred with 

 white; whilst in birds of the year the black also extends to the mantle and 

 scapulars, and the underparts are pure white. 



Young in first plumage differ from birds of the year in having a white 

 collar round the neck, and in having pale margins and brown sub-margins 

 to nearly all the feathers of the upper parts : the fork of the tail is only 

 half the depth, and the bill is brown. 



Young in down have the upper parts chestnut, mottled with black ; and 

 the underparts bufl', except the throat, which is brownish black. 



