GREGARIOUS IMPULSE 263 



return to the coast or tidal estuaries for the 

 remainder of the year. Here, at low water, they 

 find an abundant supply of food — crustaceans 

 amongst the sea-weed upon the rocks, and lob- 

 worms {Arenicola piscatoi'um) in the mud as the 

 tide advances or recedes. But when the tide is 

 full, they retire to those parts of the shore that 

 remain uncovered — to isolated rocks, or to sand- 

 dunes, or it may even be to pasture-land in the 

 neighbourhood. During this period of repose 

 large numbers of individuals gather together on 

 a comparatively small space of ground. They 

 are not constrained to do so by any shortage of 

 accommodation, nor by any question relative to 

 food, nor, for the matter of that, by any circum- 

 stance in the external environment ; they are 

 brought together solely, this at least is the 

 impression that one gains, by some inherited 

 impulse working towards that end. And their 

 subsequent course of behaviour tends to confirm 

 that impression. For if we watch the gathering 

 together of the different units of which the flock 

 is composed, and study more particularly the 

 emotional manifestation which accompanies their 

 arrival and departure, we shall find that the 

 coming of a companion arouses some emotion 

 which is expressed by a vocal outburst that 

 sweeps through the flock. 



Now each call, and the Curlew has a great 

 variety, is not only peculiar, generally speaking, 

 to certain occasions, but is accompanied by a 

 specific type of behaviour, whence we can infer 

 in broad outline the type of emotion which is 



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