108 ANIMAL LIFE OF THE BRITISH ISLES. 



vast number of Short-eared Owls appeared upon the scene and 

 feasted royally until there was scarcely a Vole to be found. It 

 was found that the enormous increase in the numbers of the 

 Voles was directly due to the warfare waged by keepers on 

 Weasels and Owls. Matters are better, perhaps, to-day ; but 

 there are still too many keepers who destroy as vermin the 

 very agents that keep down the real vermin. We still need 

 a few landowners of the temper of Charles Waterton, who 

 threatened to strangle his keeper if the latter molested a 

 certain pair of Owls. 



It was also shown at the Vole Committee of 1893, referred to 

 above, that the Rook destroys great numbers of Field Voles 

 not only adults that chance to cross the fields where the Rooks 

 are digging cockchafer grubs, but that they systematically 

 search for the nests and eat the young. 



As in the case of the Wood Mouse, there are several local 

 races of the Field Vole that have arisen in the islands of the 

 Orkneys and Hebrides, which have been elevated into dis- 

 tinct species by some recent authors. Thus, there are recog- 

 nised the Hebridean Vole, the Orkney Vole, the Sanday Vole, 

 and the Westray Vole. Mr. Barrett- Hamilton regards the 

 true agrestis of Linnaeus as not occurring in this country, 

 where it is represented by several sub-species. The Common 

 Field Vole described above, he says, is a distinct species, the 

 M. hirtus of Bellamy. This, which he describes as " a newer, 

 smaller form," he says " has replaced an older, larger M. 

 agrestis, the latter now confined chiefly to northern regions, 

 and with isolated southern colonies on the mountains." Seeing, 

 however, that most modern authorities agree in retaining the 

 Linnean name, we have considered it advisable to do so also. 



The form that Barrett-Hamilton recognises as M. agrestis 

 and calls the Northern Grass Mouse, is, so far as Britain is 

 concerned, represented only in Scotland and its western islands 

 by five sub-species which he names as under: 



