BRITISH WARBLERS
of active hostility. This is the most interesting phase of emotional reaction which I have witnessed, but then I am ignorant of what takes place when their behaviour is dominated by the sexual or parental instinct. It may be that the reactions are similar at different emotional periods, or it may be that the expansion of one wing is a particular expression of the emotion which corresponds to the instinct of pugnacity, and if this is so it is the most remarkable of all the manifestations that I have yet observed in bird life.
A feature of the bird's behaviour which arrested my attention was the general resemblance that some of its movements and some of its notes bear to those of the Whitethroat; the call-note especially is remarkably alike in the two species, but there is a difference which can readily be detected though with difficulty put into words. At times the song resembles that of the Stonechat almost as much as that of the Whitethroat, but the quiet warbling during periods of emotion might easily be mistaken for the warbling of the Whitethroat at a corresponding period. The resemblance in the behaviour of the two species is most marked in the aerial flight or dance. The Dartford Warbler springs up into the air whilst singing and remains poised as if suspended upon wires, and a similar performance is a strong characteristic of Whitethroat behaviour. But the position of the Dartford Warbler whilst in the air is somewhat different from that assumed by the Whitethroat; it is more horizontal and the wings are more fully expanded.
Much of their time is occupied in searching for food, principally amongst the heather, where for long periods they are hidden from view. They are by no means shy and it is possible to approach them closely at all times, whether they are slowly wending their way amongst the heather, or washing themselves in convenient pools of water, or singing, or even when their movements are restless and their behaviour highly emotional.
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