170 OUR BIRD ALLIES. 
the damage caused is more apparent than real, for 
the outcasts must still carry on their search for food, 
and so merely transfer their services elsewhere. 
In the second place, I need scarcely remind my 
readers that martins are not altogether pleasant 
lodgers, having tenants of their own very closely 
allied to that flat and disagreeable insect which 
can only be mentioned under a pseudonym to 
ears polite. The parasites in question, moreover, 
have an uncomfortable knack of deserting the abodes 
of their natural hosts beneath the eaves, and making 
their way through any window which may happen 
to be open below. And such unwelcome visitors, 
like their more familiar relative, are not to be ex- 
pelled without the greatest difficulty. 
Thirdly, in the struggle between sparrow and 
martin, the former bird does not seem  invari- 
ably to prove the conqueror, for cases have been 
recorded, and cases not a few, in which usurping 
sparrows have been literally walled up in their 
stolen nests by the rightful owners thereof, who 
thus have achieved by craft what by strength 
they could not perform. More writers than one 
have doubted the truth of such tales on the ground 
that no sparrow would be likely to sit still and 
allow itself to be thus imprisoned, and_ that, 
even were it to do so, a few minutes’ work would 
enable it to open a passage for its escape. But it 
must be remembered that, in the first place, a bird, 
when sitting upon its eggs, is most unwilling to 
leave them; in the second, that a creature respir- 
