1920 J The Book. 875 



upon the same kind of food in a given area; in consequence 

 the rook has taken to feeding upon cultivated crops. History 

 shows that this has happened again and again. Repressive 

 measures are taken to reduce the number of birds, and for 

 some years we hear no complaints about them injuring crops, 

 but if permitted again to increase above a certain degree, 

 they again become injurious. Therefore at the present time 

 we strongly advocate repressive measures. 



Repressive measures do not involve reckless and wanton 

 destruction ; any such unguided policy would, in all probability, 

 lead to very serious and disastrous results. A systematic taking 

 of the eggs or destruction of the nests in districts where the 

 birds are too numerous would probably be sufficient. 



If measures of this nature were put into force and carefully 

 carried out, the rook would soon assume its normal place again, 

 and it would prove to be one of the most useful birds to the 

 farmer in helping to control the larvae of such injurious insects 

 as click beetles and crane flies. 



In the absence of any census of wild birds it is impossible 

 to state with any degree of accuracy the relative abundance 

 of this species in the British Isles. Such a bird count ia 

 urgently needed for this and other species, but only where 

 there is conclusive evidence of the superabundance of the bird 

 should repressive measures be put into force, and then for only 

 a stated period. 



Twenty-one years ago the late Professor F. E. L. Beal 

 wrote: " It may be said that the damage done .... has 

 apparently arisen from the excessive number of individuals 

 rather than from the habits of the species. Thoughtful students 

 of nature have observed that every race or species has a 

 certain high-water mark of abundance, beyond which it cannot 

 rise without danger of encroaching upon and injuring other 

 species. This is true of every species, whether at its normal 

 abundance it be beneficial to man or otherwise. The 

 exemplification of this principle is most noticeable in the case 

 of insects, many species of w^hich frequently exceed their 

 ordinary bounds and spread destruction among crops. But 

 the rule is equally applicable to birds; however useful they 

 may be in a general way, it is possible under certain conditions 

 that particular species may become too numerous." This is 

 precisely what has occurred with regard to the rook in this 

 country. It has risen above the " high-water, mark of 

 abunda.nce," and in consequence has become injurious. 



