INCREASE OF ANIMAL LIFE 389 



man in conquering the wilderness. Thus cultivation has 

 increased the food and consequently the numbers of the 

 Kangaroo Rats (Perodipus and Dipodomys)of North America, 

 so that they have become a plague to the settlers. They 

 were harmless until man began to cultivate the sand-hills 

 and sage-brush country of the west, when they turned to 

 his crops, eating and storing away in burrows for winter 

 use the planted seeds of maize, water-melons and vegetables 

 to such an extent that now the only alternative to destroying 

 the animals is to give up cultivation. 



In Scotland, the effects of the growth of field and garden 

 crops on animal life, if not so striking, are still sufficiently 

 definite. To what but the cultivation of our fields do we 

 owe the great flocks of seed-eating birds which frequent our 

 stubble fields and farm-yards the Sparrows, Greenfinches, 

 Chaffinches, Yellowhammers, Bramblings, Corn Buntings, 

 Wood Pigeons and the rest? In the primitive woodlands of 

 Scotland, these seed destroyers found little room, for the 

 depths of the forest are innocent of bird life. To a limited 

 extent they may have flourished in the open ground, but they 

 and their like increased with the spread of cultivation and of 

 the seed crops which supplied them with easy nourishment, 

 and scattered until now their numbers fill the length and 

 breadth of the land. 



The increase of some of these seed-eaters, and their 

 dependence upon cultivated crops are notorious. In spite 

 of the constant warfare waged against it, in spite of the 

 annual slaughter wrought by Sparrow Clubs (one such in 

 Kent, consisting of twenty members, killed 28,000 Sparrows 

 in a single season), the Sparrow continues to increase 

 beyond bounds. Throughout the year 75 per cent, to 80 

 per cent, of the food of adult Sparrows consists of cultivated 

 grain, and the damage done to British crops by the millions 

 'of country Sparrows and the additional millions of town 

 cousins that move fieldwards at the first hint of ripening 

 grain, has been estimated by a writer in the Empire Review 

 (1917) at 500,000 quarters of cereals, valued at ,1,500,000 

 a year, though another estimate of their yearly depredations 

 places the loss at an equivalent of ,8,000,000. 



It is clear that the sparrow pestilence is due to the 

 development of cultivation, abetted, as we shall see later, 



