36 



continent and remain until Marcli. Insects, worms and molluscs 

 form its food, and in frosty weather it is frequently forced to shift 

 its quarters in search of open ground where food may be obtained. 

 The nest merely consists of a lining of dead grass in some hollow in 

 the ground, situated among rushes, grass or heather. The four eggs 

 are generally greenish-bufE, spotted and blotched, especially at the 

 larger end, with light and dark brown and grey (see British Bird Egg 

 Cabinet, drawer 20). 



Case 202. 



COMMON TERN {Sterna fluviatilis). 

 Local name : Sea Swallow. 



This summer visitor reaches our coasts towards the end of April, and 

 returns to the South between August and October. They are some- 

 what gregarious in habit, and numerous breeding stations are scattered 

 along the coasts of the British Islands as well as on inland lochs. The 

 food is mainly small fish, shrimps and other Crustacea, and like the 

 Arctic Tern it plunges into the sea after its prey. Two or three eggs 

 are laid, and they vary greatly in colour and markings (see British 

 Bird Egg Cabinet, drawer 22). They are deposited above high water 

 mark among the shingle, and their colouration as well as that of the 

 newly hatched young, closely resembles the tones of the surrounding 

 water worn pebbles. This example of protective colouration is well 

 illustrated in the group. 



ARCTIC TERN {Sterna macrura). 



This summer visitor reaches the British Islands at the end of April, 

 and departs southwards in the autumn, the migrations lasting from 

 August to October. Large colonies breed round the coasts of Great 

 Britain and Ireland, but in the north of Scotland it is most numerously 

 represented. In food and habits it resembles the Common Tern. 

 Two to three eggs are laid and vary greatly in colour markings (see 

 British Bird Egg Cabinet, drawer 22). They are laid in depressions 

 in the sand or shingle. 



LITTLE TERN {Sterna minuta). 



This, the smallest of our terns, arrives early in May, and leaves 

 in September or early in October. Its food is similar to the Common 

 Tern. The breeding stations on the flat sandy or shingly shores are 

 scattered along the coasts of the British Islands. Two or three stone- 

 coloxu'ed eggs are laid towards the end of May in hollows in the sand 

 or shingle (see British Bird Egg Cabinet, drawer 22). In the group 



