35 SECRETS OF ANIMAL LIFE 
that are sometimes seen, and who can tell us if 
there is any truth at all in the alleged “trials” 
of individuals who have defied the conventions of 
the community? It is interesting to know that the 
rook is a partial migrant, for there is a great ebb and 
flow every autumn and spring, and this may be con- 
nected with the flitting from the rookery to the 
roosting-place that we see in September. There 
may be far over a thousand nests in a rookery 
and the same site may be used for more than a 
century; and it is very interesting to have statistics 
such as Mr. Hugh S. Gladstone has given for 
Dumfriesshire, showing how old rookeries have 
waned and young colonies have grown, or to see in 
the inclosed rookeries of towns the evidence of an 
almost forgotten urbanization of the country. But 
the central interest is in the rook’s reaching forward 
to a communal life with certain conventions, and to 
the crowded nests in which we see the beginning of 
a continuous social heritage of objectively enregis- 
tered traditions, 
