292 ODD HOURS WITH NATURE 



cannot watch for any length of time a composite 

 flock of birds in a stackyard without being struck 

 by this peculiarity of conduct. They are all feed- 

 ing absorbedly. Suddenly, with a simultaneous 

 rush of wings, they are off in a compact body to 

 the bare branches of the nearest tree, from which 

 they drop back in singles and groups as their 

 fears subside. The same thing occurs again and 

 again at intervals throughout the feeding-hours, 

 and generally a visible or audible cause of the 

 movement is searched for in vain. It is much 

 easier, however, to suggest a cause there are 

 usually rats moving about than to explain the 

 simultaneousness of the flight that makes the flock 

 move as if animated by an impulse from a single 

 mind. But all this is not social action ; and, 

 indeed, it is questionable if the flocking habit 

 of the birds that make up the winter farmyard 

 flocks is a natural habit and not a by-product of 

 man-made conditions. One thing is certain : all 

 the members of the species which contribute to 

 these assemblies do not flock, for throughout the 

 winter plenty of single foragers of all of them 

 may be found about the fields and hedgerows and 

 in the gardens. Thus the congregating of the 

 birds may mean nothing more than a recognition 

 on their part of the massing in set places of food 

 supplies. It takes an effort to realize how greatly 

 human operations have modified the natural con- 

 ditions of the wild inhabitants of a country like 

 Britain, their proportions and their relations to 

 one another. To the lark, for example, we present 

 great continuous areas of land perfectly adapted 



