276 RELATION OF TERRITORY TO MIGRATION 



gregarious ihstinct again predominates, what are 

 the consequences to which this change will 

 lead ? Just as the consequences which flow 

 ixom the functioning of the former impulse are 

 accessible to observation, so likewise can we 

 observe the change that is wrought by the latter 

 impulse. The process is a gradual one. Less 

 and less attention is paid by the individual to 

 intruders, more and more is it disposed to pass 

 beyond its accustomed limits. Little by little, 

 accompanied by its young or without them, as 

 the case may be, the bird deserts its territory 

 and wanders out into the wilderness. Here it 

 associates with others, and finds in them a new 

 interest and, I doubt not, a new enjoyment. 

 All this we can observe as it takes place. But 

 just as there is an innate capacity to seek, in the 

 spring, the place where the pleasures of breeding 

 had formerly been enjoyed, so we are bound to 

 infer the existence in the adult of an innate 

 capacity to revisit the former area of association ; 

 and this capacity'; will strengthen and confirm the 

 gregarious instinct and set the direction of the 

 general course of movement. 



We have seen, then, that the interest dis- 

 played by one bird in another changes with 

 the seasons ; we have seen that it is so modified 

 as to be in useful relation to different environ- 

 mental circumstances ; as far as possible we 

 have traced out the consequences, and have 

 reached the conclusion that the change of 

 behaviour must, on the one hand, lead to 

 expansion, and on the other, to contraction ; 



