1920.] 



The Eook. 



871 



as to whether the rook is beneficial or injurious to the farmer. 

 So long ago as 1509 an Act of Parliament was passed placing 

 a price upon the head of this bird, owing to the serious injury 

 it caused to cereal crops, and the Act was revived in the reign 

 of Queen Elizabeth. 



To the farmer the question is not what a few individual 

 specimens have eaten on a particular day or in a certain district , 

 but what is the average percentage of the different food items 

 eaten during each month of the year, based on the results 

 obtained from a large series of birds, taken from different 

 districts. Once in possession of these figures he can 

 immediately form some estimate of how much damage he may 

 expect from the visitations of these birds in a year, and also 

 form an opinion as to whether this bird is beneficial or detri- 

 mental to his interests. 



Conducting our investigation on the food of the rook on the 

 lines suggested above, we are able to say, as a result of stomach 

 examinations of a number of birds, that of the total bulk of 

 food consumed in a year, 41 per cent, consists of animal 

 matter and 59 per cent, of vegetable matter (see Fig. 1). 



Further inquiry into the nature of the animal matter indi- 

 cates that there are a number of items of varying quantities: 

 thus we have 23.9 per cent, of injurious insects, 3.5 per cent, 

 of beneficial insects, 4.6 per cent, of neutral insects, 4.4 per 

 cent, of earthworms, 3.2 per cent, of slugs, snails and milli- 

 pedes, and 1.4 per cent, of field mice, young birds, and the 

 eggs of wild birds. The percentages of the different • items 

 are expressed diagrammatically in Fig. 2. 



Turning next to an analysis of the injurious insects, we find 

 that click beetles and their larvae (wireworms) form 6.5 per 

 cent, of the total, ground caterpillars 4 per cent., leather- 

 jackets 5.5 per cent., other larvae 3.5 per cent., snout beetles 

 (weevils) 3.5 per cent., and miscellaneous injurious insects 

 0.9 per cent. It is not too much to say that these constitute 

 some of the very worst and most troublesome pests with which 

 the farmer has to contend, and most of them are exceedingly 

 difficult to destroy. 



The different items and percentasfes of the 59 per cent, of 

 vegetable matter are stated in Fig. 3. 



Summarising the figures, we find that 52 per cent, of the 

 rook's food constitutes an injury to agriculture, 28.5 per cent, 

 is beneficial, and 19.5 per cent, is of a neutral nature. These 

 percentages are expressed diagrammatically in Fig. 4. 



F 2 



