Protective Coloration of the Inside of the Mouth in Nestling Birds


THE habit shown by many helpless nestlings, of gaping widely when the nest is approached, is usually explained by supposing that the birds are appealing for food. This explanation has always seemed to me inadequate, for nestlings that gape usually have the inside of the mouth brightly coloured, and in some cases marked with conspicuous spots. Moreover, newly hatched nestlings among the Passeres gape if the fingers are snapped just above them, or if the branch bearing the nest is shaken. It seems a fair inference, therefore, that the act of gaping is often, if not usually, an expression of alarm.

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BUTTERFIELD, W. Protective Coloration of the Inside of the Mouth in Nestling Birds. Nature 72, 534 (1905).

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