MARSH WARBLER
approximately the time the young Reed Warblers remain in the nest, and it is difficult to understand why, in the case of this species, the period should be increased in certain instances by three days. Climate may be connected with this variation, for development would probably be more rapid when the temperature was high and food consequently abundant. But it is well to remark that in one instance which came under my notice the young occupied the nest for close upon fourteen days, and during that period the conditions were exceptionally favourable for rapid development, insect life being abundant and the temperature abnormally high. In order to get at the truth of this variation a large number of separate pairs require to be observed.
Both sexes share in the task of tending the offspring, but one of them, as already observed, is more timid than the other, and it is therefore not altogether easy to determine just how the labour is divided; whether, that is to say, the male not only brings food and cleans the nest, but also takes his part in brooding the young. The task of brooding is performed largely, if not wholly, by the parent that is the less shy; this can clearly be seen. And since it is probable, from our knowledge of other species, that the female would naturally be more anxious to carry out this task, it is probably she who, as previously hinted at, is the less timid throughout. Yet even she is decidedly more nervous than the female Reed Warbler, for arriving at the nest with food she will remain for a long time close to, or actually upon the side of it, unable to make the final effort to deliver the food she is carrying. One or two of the young, occasionally three, are fed by one parent at a time. Their usual custom, however, is to feed two and remove the fæces from one. In the earlier stages of their growth, the young are not fed so frequently, brooding being then more important. But these conditions gradually become reversed, until the time of both parents is largely occupied in securing the necessary food. The interval between
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