GARDEN WARBLER 



cause of the abundance or paucity we are more or less 

 ignorant. The only factor we can point to with certainty 

 as affecting the question is the danger attendant on migration, 

 for large numbers must succumb annually from one cause 

 or another on the perilous journey to and from the winter 

 home, but no suggestion has yet been put forward which 

 would adequately explain so wide a fluctuation. Many subtle 

 causes might contribute towards such a result ; even a slight 

 alteration in the proportion of the sexes would influence the 

 numerical standing of a species, but I have no evidence of its 

 occurrence in Nature. 



At the commencement of the migratory movement males 

 arrive before females. The first males generally precede the 

 first females by a week or ten days, but the difference in the 

 time of arrival of the sexes is, though considerable, not so 

 great as that found amongst some migrants. Since the bird 

 is one of the later migrants to reach its breeding grounds, 

 a day gained or lost when the season is already advanced is 

 of importance, so that we should expect to find the females 

 following quickly in the wake of the males, even though this 

 were not borne out by actual observation. 



The behaviour of the species is very similar to that of the 

 Blackcap, to which it is closely related. Upon arrival at its 

 destination the male appropriates a territory and forthwith 

 proceeds to proclaim the fact by incessantly pouring out its 

 song. It would seem that some at least of the males arrive 

 during the night, for fresh arrivals are generally first heard 

 during the early hours of the morning. Of course it is open 

 to question whether these males may not have actually 

 arrived on the previous day ; they may have been fatigued or 

 hungry, and therefore not inclined to sing. Judging however 

 by the behaviour of other species, taking into consideration 

 how important it must be for every individual to proclaim its 

 possession of a territory as early as possible, and bearing 

 in mind that migration, generally speaking, does for the most 

 part occur during the night, we shall probably be right in 



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