BIRDS AND THE WEB OF LIFE 401 



toll. And wood- pigeons do great damage on the farm 

 by devouring corn and in other ways. The forester says, 

 " Fewer squirrels " ; the farmer says, " Fewer wood- 

 pigeons." One is continually confronted with the difficulty 

 of getting a " clear issue," for the circle of any animal's 

 life cuts many other circles. 



The mongoose imported to Jamaica to clear off the rats, 

 did its work well, but thereafter it had to be fed, and it 

 turned its attention to poultry and ground-birds, and to 

 snakes and lizards, some of which devour insects. The 

 thinning of the ranks of insectivorous ground-birds and 

 reptiles meant an increase of injurious insects. And this 

 is what actually happened. 



Or again, it has been pointed out that bubonic plague 

 often begins in Indian mills, where the workers eat their 

 frugal meal in the courtyard. The inevitable " crumbs " 

 attract rats, in whose blood the microbe of the plague is at 

 home. A rat-flea, with fouled mouth-parts, leaves a rat 

 and bites man, who is thus infected with the plague. If there 

 was a dovecot whose inmates would promptly look after the 

 " crumbs," there would be fewer rats, and less plague ! 



The success of sheep-farming may be linked to Pied 

 Wagtails. For successful sheep-farming depends in part 

 on the absence of liver-rot, a disease due to the parasitic 

 liver-fluke. But the juvenile stages of this worm are passed 

 within the little freshwater snail {Limncea truncatula), which 

 the Pied Wagtail is very fond of eating ! 



A few illustrations may be given of the way in which 

 birds figure on both sides of man's account. 



