BRITISH WARBLERS
ground between the two territories was, so far as one could judge, suitable in every respect for nesting purposes, yet it was passed over in rapid flight.
The daily routine of a male before the arrival of a female is simple enough, most of his time being spent in fluttering backwards and forwards between two particular trees. The males of many species have a peculiar flight of their own during the period of sexual activity, which alone makes recognition possible, and the male Wood Warbler must be reckoned amongst this number, for his slow progress between two favourite points, accomplished by moderately quick though short beats of the wings, is strongly characteristic of the species. The two other species—the Willow Warbler and Chiff-chaff, which we know well in this country, and to which the Wood Warbler is closely related—have no flight exactly comparable with this; but just as they have some special tree, or group of trees, which they make use of more frequently than another, and seem to regard as a headquarters, so this bird has two separate points with a highway connecting them. The song too forms an important part of this particular aspect of behaviour, since at no other time is it uttered so frequently or so regularly. But we do not find the bird always thus employed. There are periods of varying lengths when it is engaged in searching for food high up in the tree tops or low down amongst the bushes, and it is just at these times that it roams farthest from its central position, and, journeying thus, forms a habit which justifies the application of the term "boundary" to the normal limit of its wanderings. In the districts in which my observations have been made, the birds are plentiful enough, though not nearly so numerous as the Willow Warbler or Chiff-chaff; so that the conditions which lead to overcrowding and competition have never been very present to my experience. I have never, that is to say, witnessed much rivalry between different individual males, but sufficient all the same to show that they are just as anxious to defend
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