256 THE SCOTTISH NATURALIST 



in good stead for so many years. To the outsider it seems 

 that each method has good qualities of its own, and that 

 the volumetric method, while offering an opportunity for 

 facile graphic representation, is for various reasons no less 

 infallible than its predecessor. The numerical method on 

 the whole emphasizes the destruction of the lesser items 

 insects and seeds ; the volumetric method emphasizes the 

 destruction of bulky food, such as fruit, potatoes, turnips, 

 and the like. But the final decision of the economic value 

 of any particular bird must rest, not on the patent proportions 

 of its food, injurious or beneficial (proportions interestingly 

 rendered in graphic form in Dr Collinge's paper), but on a 

 subtle interpretation of these proportions, which endeavours 

 to assess in the case of each item its ultimate economic 

 value. So far as we can see, there is no scientific check 

 upon this all-important interpretation it depends upon 

 the idiosyncracy of the interpreter ; and it is because the 

 numerical method of estimation affords a possible basis for 

 a definite statistical reading of economic values that we 

 feel this old method should not lightly be cast aside. 



In the cases of the majority of the birds discussed by Dr 

 Collinge in the paper before us, the decision, for or against, 

 is easily made on the statistics he supplies, and confirms the 

 general opinions long held by naturalists. In face of these 

 statistics, which we take for granted are based on fair 

 samples, no one can doubt that the Lapwing, 60 per cent, of 

 the volume of whose food consists of injurious insects, or the 

 Kestrel with its 64-5 per cent, of mice and voles, or the 

 Green Woodpecker with its 75 per cent, of harmful insects, 

 or the Skylark with its 43-5 per cent, of weed seeds and 

 another 35-5 per cent, of injurious insects, perform outstand- 

 ing service to the farmer. In the areas where these statistics 

 hold true the landlord and farmer could not do better than 

 afford these species every protection in his power. But, we 

 imagine, the numbers are not applicable to all areas, for 

 the 1 per cent, of "leaves" consumed by the Skylark can 

 scarcely be taken as representing its depredations say in the 

 agricultural districts of Gloucestershire, where it does serious 

 damage every year to sprouting grain-crops and grass. 



