GARDEN WARBLER 



source of irritation, and that the behaviour thereby falls into 

 line with that which is commonplace in the lives of other 

 species, is not without significance. Instances of such 

 antagonism have already been referred to. Whenever two 

 closely allied forms, requiring similar conditions of existence, 

 come into touch with one another, there we so often find 

 evidence of the inevitable struggle for existence. We are 

 thus led back to the question of breeding territory. The 

 Garden Warbler and the Blackcap inhabit a similar environ- 

 ment, require similar food, and, like the Willow Warbler and 

 Chiff-chaff, probably compete with one another; for where 

 both species are abundant, conditions must at one time or 

 another arise which will give a slight advantage to the one 

 that through superiority in some direction is better able to 

 ensure an adequate supply of food for its offspring. I believe, 

 therefore, that these scenes which we witness are but the 

 expression points of this struggle for territory, and further 

 that we can explain in the same way those violent outbursts 

 of song which are coincident with the other manifestations 

 of excitement, and are often the prelude to a conflict. The 

 violent use of the vocal powers when the Garden Warbler and 

 Blackcap come into contact with one another is sometimes 

 ascribed to a cause other than that which we are here suggest- 

 ing; the song itself is regarded as the principal feature, 

 and an appreciation of their vocal powers by the birds as 

 the stimulus to the outburst. But if song has a meaning 

 in relation to the question of territory, we have in this fact 

 a more simple explanation, the term "song" being held of 

 course to include sounds of all descriptions produced under 

 these peculiar circumstances. From the biological stand- 

 point, there is no difference between the monotonous call 

 uttered by the Green Woodpecker whilst occupying his special 

 tree morning after morning, and the passionate but beautiful 

 outburst of the Blackcap. The song is only one of a series 

 of activities which work towards the goal of reproduction. 

 Through it the females are enabled to recognize and locate 



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