Natural History 413 



and great power of vocalisation which may develop to a remark- 

 able extent. Experts tell us that the Rook has command of be- 

 tween thirty and forty notes. To learn to what extent they employ 

 them one has only to listen to "the black republic in the elms," 

 after the breeding season is over. 



Professor J. Arthur Thomson, hi Secrets of Animal Life, 

 says: "Like many creatures well endowed with brains, rooks ex- 

 hibit what must be called play. There are gambols and sham 

 fights, frolics and wild chases, in which, curiously enough, jack- 

 daws and lapwings sometimes become keenly interested. But 

 who knows the real truth about rooks posting sentinels, which is 

 so often alleged? Who knows the significance of the vast con- 

 gregations 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? . . . But the central 

 interest is in the rooks reaching forward to a communal life with 

 certain conventions, and to the crowded nest in which we see the 

 beginning of a continuous social heritage of objectively enregis- 

 tered traditions." There may be far over a thousand nests in a 

 rookery, and the same site may be used for more than a century. 



Rooks certainly have a considerable vocabulary. There is 

 not, indeed, any language in the strict sense man has a monopoly 

 of that; but the rooks have words just as dogs have, definite ut- 

 tered sounds which have definite meanings. We hear the rooks use 

 certain words when we move suddenly beneath the trees, and other 

 words are uttered when a bird intrudes on its neighbour ; there is 

 a word when the rook sinks down upon the nest, and another word 

 when it flies clear of the rookery and makes for the fields. What 

 danger-signals, what scoldings, what chucklings, what exultation, 

 what reproaches, what encouragement do we not hear? 



Mutual Protection 



Mr. W. P. Pycraft, in his History of Birds, says : "Among 

 gregarious species some display a much more intimate association 



