BRITISH WARBLERS 



only to watch the oak trees when the larvce of the Tortrix 

 viriclana are hatched to see the truth of this, for quantities 

 of Blackcaps, Garden Warblers, Willow and Wood Warblers, 

 and Chiff- Chaffs there find a living, or the alders adjoining 

 some reed bed which, when the aphides are swarming, 

 attract numbers of Eeed and Sedge Warblers, Chiff-Chaffs, 

 Willow and Garden Warblers. There remains the emotional 

 behaviour upon which opinion is so divided. The continuity 

 which we can almost trace in structure and instinct fails 

 us here, and in place of it we are faced with facts of that 

 contradictory kind which nature so often reveals. Those two 

 small birds, perched on the same branch within a few feet of 

 one another, flapping their partially expanded wings, we know 

 at once to be a pair of Willow Warblers, for the Chiff-Chaff 

 behaves differently. That bird, which rising from the hedge 

 dances in the air as if suspended by an elastic thread, w 7 e 

 recognise without difficulty, since its nearest of kin the Lesser 

 Whitethroat has other means of expressing its emotions. 

 And similarly we distinguish the Blackcap from the Garden 

 Warbler, for each during times of excitement spreads out its 

 wings and tail and raises its feathers in certain ways peculiar 

 to it. Yet we cannot by such means distinguish between the 

 Grasshopper and Savi's Warblers ; their actions are identical ; 

 they spread and move their wings similarly, and if it were not 

 for the difference in colour and in the pattern on the feathers, 

 or the much more musical trill of the one, no one could say 

 with certainty whether the bird he was observing belonged to 

 this or to that species. Here is a somewhat different case. 

 Let us imagine ourselves in the centre of some reed bed 

 towards the end of May. Beed Warblers are all around. 

 Beside us is a male, evidently sexually excited, uttering its 

 metallic sounding song, and whilst doing so jerking its wings 

 slightly outwards from the shoulder. Leaving it we enter an 

 osier bed from which a more beautiful, more highly developed 

 song is proceeding. To all appearances the owner of the 

 voice is a Beed Warbler; it too is excited, singing to the 



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