140 Instinct, 



for their young without aid from others, but at the 

 time of rearing young, the flock is generally broken 

 up, each pair caring for its own. It is after the 

 breeding season is over and the young are able to 

 shift for themselves, that flocks and herds are form- 

 ed among many of the social birds and beasts. 

 This may, in some cases, be done simply from love 

 of society. Here the work of Instinct seems to be 

 simply to increase enjoyment. But in very many 

 cases, perhaps ultimately in all, there is a certain 

 organization of the flock ; and that organization 

 is made in some way subservient to the welfare of 

 the individuals, as such. The most simple case of 

 united action, is in following a leader. There seems 

 to be, in flocks of animals of various kinds, some in- 

 dividual that leads either in migration or in de- 

 fence. This leader is generally the most powerful 

 male of the flock. But another advantage to the 

 individual, from the flock organization, is seen in 

 the selection of sentinels, that are posted to give 

 warning, while the others feed. Among common 

 fowls, each one is ready to give warning of danger ; 

 but among many wild animals there is often coop- 

 eration according to a system, and a very excellent 

 system too. Crows and Pigeons may be seen watch- 

 ing upon the trees, while their fellows feed in the 

 meadow. At the approach of danger, these senti- 

 nels raise the alarm which is the signal understood 

 by every one of their mates. Those that watch in 

 the beginning, are from time to time relieved, while 

 others mount guard in their places. It is impossi- 

 ble to tell how it is arranged, that the distribution 



