GREGARIOUS IMPULSE SERVICEABLE 269 



behind it, sees at one moment the right eye 

 and at another the left. No movement of the 

 feet or of the legs is perceptible, and the shifting 

 of the body continues whether the eyes are 

 open or closed. This body movement enables 

 the bird to survey a much larger area of ground 

 than it would otherwise be capable of doing, 

 and thus adds to its security. As far as my 

 experience goes, the movement is less evident 

 amongst the members of a flock than when 

 an individual is resting, alone, or even with a 

 few companions, which may be due to the fact 

 that since some members are always awake 

 and watchful, a bird of prey would have more 

 difficulty in approaching a flock unawares than 

 it would have in approaching a single individual. 

 With the greatest ease a Sparrow-Hawk can 

 pick up a Thrush as it feeds on the meadow 

 by itself, but if it attempts to seize one of a 

 flock, the chances are that its approach is 

 signalled and that its prey escapes. And not 

 only do the different members give warning 

 one to another of the approach of danger, 

 but they also combine to harass or even to 

 drive away an enemy. So that there can be 

 no doubt that the gregarious instinct is service- 

 able in promoting the welfare of the race, and 

 has, as its end, the preservation of the individual 

 in order that it may take its share at the 

 appropriate time in procreating its kind. 



In winter, then, the individual loses its 

 individuality and is subordinated to the welfare 

 of the community, whilst in spring it regains 



