Page:The British Warblers A History with Problems of Their Lives - 2 of 9.djvu/44

 is approached. This varies according to the situation, but in most cases the remarkable tendency towards fixed habits, of which I shall speak presently, is in evidence. On her way to the nest she glides each time under the same bramble, perching always on the same twig, and when hidden from view her progress can still be marked by the same leaf shaking here, or the same nettle swaying there, until the nest is finally reached and her entrance disclosed by the usual movement of twigs around. Why this careful approach? Can it be for the better protection of the young? Is it, therefore, a means to an end? These are difficult questions, but perhaps the best reply is in the way in which she leaves it; for instead of doing so in the same careful manner, she flutters out through the foliage and undergrowth, making such a rustle as would ensure her movements attracting attention.

For so small a bird the young are a long time before they are fledged sufficiently to leave the nest, the exact time being about fifteen days after the first young one is hatched.

I have sometimes speculated as to why the nestlings of some species develop more rapidly than those of others. Is there any difference in this respect between those species that build open nests and those that do not? Is the slow development confined to those species in which one parent bird only supplies food? If these questions can be answered in the affirmative, then we may attempt to explain either the indolent habits of some males, or the habit of building covered nests, by simple cause and effect; but I have not had sufficient time to investigate it fully.

Until the young are able to follow their parents properly, they keep low down in the bushes and undergrowth, often even on the ground. This must be an anxious time for the mother, as enemies abound, and the young are generally scattered. However, after a few days, being able to fly with rather more strength, they gather together again and keep higher up in the trees; and now they can often be seen