BRITISH WARBLERS
and as to the period during which the eggs are laid the species does not seem to differ, on the whole, from others closely allied, one being laid as a rule every twenty-four hours. The behaviour of the male, directly the first egg is laid, is interesting, as he at once takes his share in sitting upon and maintaining it at the proper temperature. Judging from their actions incubation proper does not commence until the fourth or fifth egg—according to the number of the clutch—is laid; for directly the full number is completed their anxiety not to leave them too long exposed is very apparent. I have taken particular notice of the behaviour exhibited by the sexes during the period of incubation, and it does not seem to me to show any very striking difference. Nineteen minutes is the longest period I have recorded that the female has remained upon the eggs, and seventeen minutes in the case of the male. The one leaves the nest immediately upon the appearance of the other, and the male will sometimes sing on the way to the nest, and even while on the nest itself. The female utters a low quiet note as she approaches and is desirous of replacing her mate, and whilst sitting upon the nest pecks at and appears to be arranging the material in the interior. There is a difference—but whether such difference is constant, or happens only to have been the case in those instances I have had under my notice, it is impossible to say without further investigation—in the direction in which the sexes face while incubating; each one seems to have its own particular direction, which it adheres to with more or less regularity.
Incubation lasts fourteen days, calculating from the day upon which the last egg of the clutch is laid; and as soon as the young are hatched the parents become decidedly more anxious, betraying uneasiness in their movements. Of the two the male is the more nervous, approaching the nest with great timidity and only with difficulty overcoming his alarm at one's presence. But, as already mentioned, the excitement displayed by the species as a whole, both at this and other
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