198 ANNALS OF SCOTTISH NATURAL HISTORY 



uncertain as to the value of rooks as destroyers of full- 

 grown voles, as I had watched them repeatedly through 

 good binoculars, without result. But the point has been put 

 to rest by Mr. Martin, Bowhill, who shot five rooks at 

 Tushielaw, in Ettrick, and three on Dryhope, in Yarrow, and 

 found that the birds had been feeding on old as well as 

 young voles. Mr. Martin has several times seen Black- 

 headed Gulls rise out of a meadow with voles, so close that 

 he could hear the vole " squeak " and see it " wriggle." The 

 Buzzard is so scarce and local on these uplands as not to 

 deserve much notice. But on the farms frequented by a 

 stray bird or two, the shepherds have unbounded faith in its 

 virtue as a vole-killer. 



Of the part taken by the Stoat and the Weasel in the 

 work of destruction, little information can be obtained. The 

 only point certain is that, during the plague, few were visible, 

 though now they are showing themselves. Our view is that, 

 while the voles were in plenty, they got their food so quickly 

 and so abundantly that they never required to be much out 

 of their accustomed quarters. 



The present has been truly an instance of the birds of 

 prey flocking to the carcase ; and when the numbers and 

 rapacity of the horde which gathered together are taken 

 into account, it may fairly be assumed that they were a con- 

 siderable factor in the gradual disappearance, and the final 

 extermination of the Vole. 



Mr. Robert Service, whose views are of very great value, 

 is of opinion that the plague was due to a set of favourable 

 and very unusual weather conditions, leading to abnormal 

 reproductive power ; and while giving due weight to the 

 ravages of natural enemies in bringing the plague to a ter- 

 mination, considers that the principal factor was " the loss of 

 those abnormal powers of increase, which, until they ceased, 

 no number of natural enemies ever likely to be present could 

 have coped with." 



The effects of the disappearance of the Vole on the Short- 

 eared Owl and the Kestrel have been disastrous. The Owl 

 began to nest last spring as early as February ; but the nests 

 on the various farms were very much below the numbers of 

 the spring of 1892, so far as we have learned, except in four 



