284 RELATION OF TERRITORY TO MIGRATION 



and the impulse to seek isolation comes into 

 functional activity. What the organic condition 

 is and how it arises we do not exactly know ; 

 all we know is that organic changes do take 

 place in the breeding season, that these changes 

 profoundly modify character, and that they 

 correspond with the seasonal growth of the 

 sexual organs. And with regard to the question 

 of stimulation, we have again to confess to 

 much ignorance, although certain facts are pre- 

 sented to observation which seem to indicate 

 the direction in which the stimulus lies. For 

 example, it is well known that abnormal climatic 

 conditions influence behaviour ; we see migrants 

 retracing their flight along the very course they 

 travelled a short time previously driven head- 

 long by the blizzard, that at least is what w r e 

 say. But if the wind, instead of being cold and 

 from the north, is warm and from the west, do 

 they retrace their flight ? I have not found it 

 so. And if there be no wind and the tempera- 

 ture is low, are they still affected? Again, I 

 have not found it so. When, as we commonly 

 say, they fly before the storm, some change 

 takes place in their organic complex, some new 

 impulse receives stimulation or the former one 

 lacks it. If, after Lapwings have established 

 themselves in their territories, the weather 

 becomes exceptionally severe, the birds collect 

 together again in flocks and revert to their 

 winter routine ; and under similar circumstances, 

 Buntings fail to sing and temporarily desert 

 their territories. In such cases it is clear that 



