54 OUR BIRD ALLIES. 
parental, and the birds leave their young rather 
than remain behind after their companions have 
taken their departure. It is far from unlikely, there- 
fore, that such belated sojourners as have from time 
to time been noticed were deserted birds, which had 
managed for a time to pick up a scanty livelihood, 
their parents having left them just as they were able 
to fly, although not yet sufficiently strong to undertake 
a journey across the seas. 
More familiar even than the swift is the White- 
bellied Martin, whose domiciles of clay beneath the 
eaves are so great an eyesore to many householders. 
For the bird is one of those which are strongly 
attached to human _ habitations, and which are 
seldom to be found far away from the abodes of 
man. Year after year a pair of martins will return 
to the same _nesting-place, and, if unmolested, will 
become so tame as to carry on their domestic 
arrangements within a foot or two of a window belong- 
ing to a room in constant use. Every now and then, 
however, some suitable cliff or especially attractive 
rock overcomes their repugnance to solitude, and 
such favoured spots are to be seen literally studded 
with the little edifices in which the bird brings up 
its young. 
The material of which these nests are composed 
consists principally of the fine earth which is thrown 
up in the form of “‘ worm-casts,” and which, moistened 
by the bird’s saliva, is carefully kneaded until of a 
proper consistency for building purposes. |Some- 
