a kind of plaster. There seems no doubt at all that the 
building site, once chosen, is used by the same birds year 
after year, three or even four broods of little ones being 
hatched out in the course of a season, The later ones, 
however, do not always reach maturity, and cases are not 
unknown in which they have been left in the nest unfledged 
when the time came for the parents to set out on their 
autumn migration, and their dead bodies unconcernedly 
pulled out and thrown away when they returned in the 
following spring. The eggs are glossy white in colour, 
without any markings. 
Closely related to the house martin is the Sand Martin, 
which can easily be distinguished by its smaller size, and the 
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