WILLOW WAEBLER 



adults, even appropriate the old territory, but what is of more 

 concern to us is the extent to which they do so. Is it a rule 

 for the same male to return to the same territory ? And does 

 the female seek her former mate ? These are the questions 

 which w r e should like to be in a position to answer, and they 

 are questions to w T hich I have never been able through 

 actual observation to obtain a definite reply. The marking, 

 of young birds may tell us whither they go, and whether 

 they return to the locality of their birthplace, but upon 

 the point in question it can clearly throw 7 no light unless 

 some system can be devised whereby the owners of certain 

 territories are annually caught and released. In the case of 

 some of the migrants males are the first to reach their desti- 

 nation, afterwards the sexes arrive intermingled, but not 

 paired. A male takes up its territory and there awaits a 

 female, upon whose arrival pairing takes place. The young 

 are then hatched, and as soon as they are capable of taking- 

 care of themselves the parents desert their territory and 

 appear to separate. Will they again meet the following 

 breeding season ? Is it likely, in the first place, that both 

 will survive ? We have no direct evidence to guide us in 

 estimating the average duration of life of an individual under 

 natural conditions, but w^e can be certain that it varies 

 enormously in different species. However, w^e are here con- 

 sidering the migrants only ; and bearing in mind the mortality 

 which must and does occur amongst them during migration, 

 from scarcity of food, from vagaries of climate, from disease 

 and from natural enemies, and fixing our attention on the 

 fact that there is no perceptible increase in their numbers year 

 by year, how can w T e regard such an existence as otherwise than 

 a precarious one ? And are not the chances, therefore, of both 

 surviving somewhat remote? Assuming, however, that both 

 escape the numerous dangers that threaten them, and are 

 consequently capable of breeding the following spring, will 

 both male and female steadfastly make their w T ay back to 

 the same few acres of ground which they inhabited the 



7 



