264 RELATION OF TERRITORY TO MIGRATION 



aroused. Thus we come to recognise fear, anger, 

 or sexual emotion, by just the particular sound 

 which is emitted. But even if we are going 

 too far in referring particular calls to particular 

 emotions, we can, without a doubt, divide them 

 into two broad categories those which are 

 pleasurable and those which are the reverse. 

 And we need have no hesitation in placing the 

 particular call to which I allude in the first of 

 these two categories, not only on account of the 

 nature of the sound produced, but because the 

 activities which are aroused are not such as 

 normally accompany irritation. This is well 

 seen if the behaviour of different individuals 

 be closely observed. After resting on one leg 

 for some time, first one and then another is 

 seized with cramp, and running a few yards 

 in an ungainly way, bumps up against its com- 

 panions as if it had not full control over its 

 movements. Its behaviour produces irritation 

 which is expressed by a vocal outburst, and 

 followed by actions the meaning of which is 

 clear. Moreover, the call is taken up by 

 other individuals and sweeps over part of the 

 flock as does the greeting. But the nature of 

 the cry is entirely different from that which 

 greets the arrival of a companion humanly 

 speaking it is a passionate and impatient utter- 

 ance, the height of displeasure. The arrival, 

 then, acts as a stimulus to something in the 

 inherited constitution which is expressed in, and 

 presumably is satisfied by, this vocal outburst ; 

 and, since the bird that arrives joins also in the 



