BRITISH WARBLERS 
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 
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