{Lams ridibundus) remove the empty eggshell shortly after the hatching of the chick. An investigation into the survival value of this response and of the stimuli eliciting it (Tinbergen et al. 1962a) yielded the following results. An empty egg-shell at a distance of four inches from a single egg laid out in the dunes rendered such an egg more vulnerable to predation by Carrion Crows (Corvus coroni...

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