346 THE ROLL OF THE SEASONS 



Mr. Hudson, travel far in order to dig out their neigh- 

 bours who have been buried in their township by the 

 ranchers of the pampas. There is a favourite corner 

 of the field below the garden where we can always 

 find a colony of voles. They drill their neat holes 

 very near to one another, but rarely, if ever, share a 

 common entrance. It is difficult to see how they gain 

 by this colonising habit, while the kestrel by day and 

 the owl by night find their work comparatively easy, 

 thanks to the hunting-ground being so circumscribed. 

 Probably there is a sentinel, delegated by the com- 

 munity, or self-appointed, usually ready to give warn- 

 ing from which all the others may profit. More likely, 

 the hourly sacrifice of one of the voles is cheap 

 because it scares hundreds instead of few or none, as 

 it would do if each vole family lived apart. Twenty- 

 four casualties a day may seem a heavy toll, and is, 

 no doubt, in normal times seldom reached, but when 

 a large colony is bringing forth its thousands of young 

 every week, it can stand a far greater drain and still go 

 on increasing to plague dimensions. In the great 

 Scottish vole years of 1901 and 1902 the local owls 

 were reinforced by hundreds of the short-eared species 

 from the Continent, which nested there and reared 

 several broods of young in a single season, some of 

 them with twice the usual number of chicks. It was 

 a superb battle of mice and birds, though it is not 

 certain that without the intervention of man the birds 

 would have won. Most probably so, however, for, 

 while more mice led always to more owls, they also 

 meant less grass, and thus fewer and weaker mice to 

 withstand more and hungrier enemies. We are 

 content to have the balance perennially even, or oscil- 



