THE COMMON ROOK. 
131 
portion consists of this injurious plant. The object of 
the bird in performing this service for us is to obtain the 
larvae of several species of insects, underground feeders, 
that prey on the roots, as Linnaeus long ago observed 
upon the subject of the little nard grass (nardus stricta). 
This benefit is partly a joint operation : the grub eats 
the root, but not often so effectually as to destroy the 
plant, which easily roots itself anew; but the rook 
finishes the affair by pulling it up to get at the larvae, 
and thus prevents all vegetation ; nor do I believe that 
the bird ever removes a specimen that has not already 
been eaten, or commenced upon, by the caterpillar. 
The rook entices its young from the breeding trees, 
as soon as they can flutter to any other. These youngs 
for a few evenings after their flight, will return with 
their parents, and roost where they were bred; but 
they soon quit their abode, and remain absent the whole 
of the summer months. As soon however as the heat 
of summer is subdued, and the air of autumn felt, 
they return and visit their forsaken habitations, and 
some few of them even commence the repair of their 
shattered nests ; but this meeting is very differently 
conducted from that in the spring ; their voices have 
now a mellowness approaching to musical, with little 
admixture of that harsh and noisy contention, so dis- 
tracting at the former season, and seems more like a 
grave consultation upon future procedure ; and as winter 
approaches they depart for some other place. The 
object of this meeting is unknown ; nor are we aware 
that any other bird revisits the nest it has once forsaken. 
Domestic fowls, indeed, make use again of their old 
nests ; but this is never, or only occasionally, done by 
birds in a wild state. The daw and rock pigeon will 
build in society with their separate kindred : and the 
former even revisits in autumn the places it had nestled 
in. But such situations as these birds require, the ruined 
castle, abbey, or church tower, ledge in the rock, &c., 
are not universally found, and are apparently occupied 
from necessity. The rooks appear to associate from 
preference to society, as trees are common everywhere ; 
but what motive they can have in view in lingering 
