Ihe Uathenng ot the Clans. 267 



some were used for so long a time that to this day 

 they have not recovered their fertility, the applica- 

 tion of patent plant-food even availing little. 



Why do they congregate in such numbers ? It 

 has been suggested that in early autumn their food 

 was to be found only in limited localities, and they 

 naturally drifted there, moved, one and all, by the 

 same cause. In other words, the upland fields, the 

 spring-holes, the grassy nooks in old field-corners, 

 where they nested, offered nothing but shelter, and 

 to stay longer than during summer meant to starve. 

 The fact that scattered birds do frequent the nest- 

 ing-places contradicts this; and the food found in 

 the meadows is not greatly different, and often too 

 many gather in one spot for all to be fed. What- 

 ever the bird, there seems to be nothing gained by 

 flocking, and much is lost. It appears to be an 

 inherited instinct that, once a source of delight and 

 unattended with danger, is now, as ever, attractive, 

 but directly disadvantageous. 



We are accustomed to look upon certain species 

 of birds as flocking in autumn, and that others 

 never do so. I am convinced that all were gre- 

 garious originally, but changes of environment 



