38 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. 



