^74 BRITAIN'S BIRDS AND THEIR NESTS. 



Where a sheltered site has been chosen, the same nest 

 may last for years and be used over and over again. In 

 such cases only a few repairs are needed, but often a 

 new nest has to be built, and this takes nearly a fort- 

 night, a layer about half an inch thick being added each 

 morning, and left to dry and harden for the rest of the 

 day. 



Clinging to the roughness of the wall or rock, and 

 leaning part of its weight on its tail, the bird doubtless 

 uses in most cases some irregularity of the surface on 

 which to establish the foiuidations of its nest. But that 

 «uch a support is not absolutely necessary is shown by a 

 recent remarkable case of a Martin which built its nest 

 against a vertical pane of smooth glass. What keeps the 

 nest in position in such cases baffles explanation. It has 

 been suggested that the Swallow and the Martin may 

 employ some salivary fluid like that of the Edible Swift- 

 lets of the East, but the necessary glands have not been 

 proved to exist. 



After the outer shell of the nest has been completed, 

 it is a familiar sight to see the Martin catching flying 

 feathers. These, with pieces of straw, form the lining on 

 which the four or five eggs — pure white, not spotted like 

 the Swallow's — are deposited. The eggs are laid at the 

 rate of one a day, and are then incubated for a fortnight. 

 The young are at first blind, helpless, and practically 

 naked ; but when they leave the nest three weeks later — 

 almost full-grown, and stronger on the wing than most 

 nestlings — they have a plumage resembling that of their 

 parents, but lustreless brown instead of glossy black, and 

 altogether duller. 



In July a second clutch is laid, and the finding of young 

 still in the nest in October may be taken as evidence 

 that the Martin sometimes has three broods in a season. 



