416 BRITISH BIRDS. 



destroy carrion on the sea-shore and on land, and to keep 

 in check the voles and field-mice, which they devour in 

 numbers. They must, however, be recorded amongst our 

 harmful species. Yet it is doubtful if it is wise to persecute 

 them too far, for then we get rabbits and small mammals 

 increasing to excess. 



The Rook {C. ffur/ilerjus) is, on the other hand, very bene- 

 ficial. The rook can at once be told by the white mark at the 

 base of the bill. Moreover, the rook is gregarious, flying about 

 and nesting in large companies. The main food of the rook 

 consists of insect grubs, especially wireworm, leather-jackets, 

 and cockchafer larvae. Wherever we see rooks collected in the 

 fields, there we have a sure sign of insect infestation. !Never- 

 theless they are often ruthlessly destroyed, for it is said they 

 do so much damage. "What damage do the rooks do ? They 

 pull up roots and leave them dying on the ground, they eat 

 grain, and they carry oif large numbers of walnuts. Certainly 

 in the last two instances they are harmful, but not to any great 

 extent. The plants they pull up are not pulled up out of pure 

 mischief, but to get at the wireworm biting at the roots ; this 

 they devour : they thus destroy one turnip and one wireworm. 

 How many turnips and other jilants would the wire'.\orm 

 destroy in its three or even five years of life? Some hundreds 

 of thousands, and thus by killing the pest the rook must be 

 saving all those future doomed plants that come in the wire- 

 worm's way. It is said that there are too many rooks, and thus 

 their number must be kept down. This cannot be correct. 

 If rooks are injurious, then kill them off entirely. It costs no 

 more to scare 1000 rooks than 10. If 10 do good, then 1000 

 do so much more. Moreover, grain can be well preserved by 

 mixing the seed with tar. If rooks and the like are killed we 

 should have but little corn, for man cannot control, as yet, soil- 

 grubs in the field. 



The Jaclrluw (C. moupdiila), which is much smaller than the 

 rook and told by the grey colour of the back of the head and 



