BRITAIN'S BIRDS AND THEIR NESTS. 209 



colonies, even a few miles apart, may be quite different, and 

 it has been suggested that the birds of a colony probably 

 remain banded together in their winter-quarters and on 

 their migrations. 



Exceptionally a Swift has been recorded in England as 

 early as the end of March, but usually it is late in April 

 before the species appears even in the south, and well into 

 May ere it reaches Scotland. From the time of its arrival 

 it is fairly abundant and widespread in the British Isles, 

 except in the extreme north of Scotland and its outlying 

 islands. From the whole country it has usually disap- 

 peared well before the end of August, an extraordinarily 

 early date. 



Within this short period only one brood can, as a rule, 

 be reared. Sometimes a second is attempted, but if the 

 young are not ready by the time of emigration they are 

 abandoned to their fate. About a month after the birds' 

 arrival the eggs are laid in a nest composed of straw, 

 feathers, and the like, snatched up as they blow about. 

 These are glued together with a fluid secreted by the 

 birds, a fact which reminds us of the ' edible nests "■ built 

 by the Swiftlets of the East. The situation is generally 

 a crevice of some sort, whether under the eaves of a house, 

 in a church tower, in a ruined castle wall, in a precipitous 

 cliff, or even in a hollow tree or other unusual place. 

 The eggs are two in number, pure white in colour, long 

 and oval in shape, and rather rough of surface. Eighteen 

 days are needed for incubation. 



The 'night-flying' of the Swift is an extraordinary 

 phenomenon, which has attracted much attention, but still 

 remains a mystery. Towards nightfall, unusual signs of 

 activity may generally be noted among the Swifts of a 

 nesting colony, and soon they band together for one last 

 dash round the neighbourhood. On this they go faster 



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