EEITISE WARBLEBS 



namely, why, in the case of two such closely allied forms living 

 in a similar environment, one should arrive at its breeding- 

 ground so much in advance of the other. 



The law of breeding territory forms as important a part in 

 the life-history of this bird, at this particular season, as it does 

 in that of so many others. Similar conflicts occur, similar 

 petty struggles ; in fact, the whole routine of the life of the 

 male, previous to and after the arrival of the female, may be 

 said to be almost identical with that of the male Chiff-chaff. 

 Inasmuch, however, as this law seems to be one of some 

 importance in the life of many species of birds, and possibly 

 other vertebrates, I shall describe minutely any details that 

 have come under my notice bearing upon the question, no 

 matter how small or perhaps even trivial they may seem, and 

 no matter how similar to those in the life of the Chiff-chaff or 

 any other species already dealt with. In order to observe 

 the behaviour of the birds during this period, it is as well 

 to select some wooded bank inhabited by a number of males 

 and divided into a number of adjoining territories. For such 

 territories are never very large — although they vary consider- 

 ably in extent, being perhaps twenty-five, forty, or sixty yards 

 in length — and consequently it is by no means impossible to 

 keep three adjoining areas under observation at the same time, 

 which is an advantage and often an assistance in enabling one 

 to interpret the actions of the different inhabitants. Moreover, 

 where possible, the same wooded bank or plantation should be 

 selected for two or three years in succession, since by this 

 means alone is it possible to discover through actual observa- 

 tion whether the same males return to the same territories 

 year after year; and besides, by so doing, one commences 

 each season with a considerable and important knowledge 

 of the previous life-history of the various inhabitants of 

 that particular locality. As to whether the same males do 

 return to the same territories we know very little. There 

 are certain authenticated facts which show that birds do 

 sometimes revisit their birthplace, and, in the case of the 



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