WILLOW WARBLER 



to say that the same male and female never meet — since 

 according to the law of chance a reunion must in some 

 instances take place — but to lay it down as a rule that the 

 same individuals meet again and again in consecutive seasons 

 and are consequently paired for life is a different matter, for 

 there could be no rule of that kind unless some useful purpose 

 were thereby served. Inasmuch, however, as the fact that the 

 sexes arrive at the breeding area separately admits of no 

 dispute, and since there is every reason to believe that a 

 similar condition accompanies their departure to the feed- 

 ing area, it is evident that they are united for part of the 

 year only, and whatever reunion does occur in the breeding- 

 season must be in the nature of a casual meeting, having, as 

 we have already seen, little to recommend it as a conditio sine 

 qua non to the pairing of the stronger individuals. In almost 

 every part of these Islands and probably in almost every part 

 of civilised Europe the breeding stations of most of the 

 migratory species are constantly changing. The timber is 

 felled and the undergrowth cleared in some wood, and the 

 following spring it possesses no attractions for the smaller 

 migrants, since the new growth is insufficient to provide them 

 with shelter. But as the seasons pass by and the growth 

 increases, more and more individuals of various species take up 

 their territories until the whole wood becomes an important 

 breeding station resonant with the song of many migrants. 

 Slowly the bushes entwined with bramble and honeysuckle, 

 which used to afford shelter for innumerable nests, increase in 

 stature, pass into saplings, and ultimately check the grow T th 

 of vegetation beneath, and correspondingly the number of 

 migrants resorting thereto for the purpose of reproduction 

 decreases, until the wood reverts, so far as they are concerned, 

 to its previous state of destitution. Somehow and somewhere 

 these former inhabitants must obtain territories. Urged by 

 their sexual instinct they will wander from place to place 

 seeking a new home, and find, perchance, a resting place in the 

 same locality or possibly suffer banishment from the immediate 



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