Coots count

摘要

American coots distinguish their own eggs from the eggs that other female coots lay in the same nest. They use a variety of tactics to minimize the adverse reproductive effects of the parasitic behaviour. Cuckoos are infamous for laying their eggs in the nests of other bird species: the unfortunate hosts raise the parasitic chicks, reducing or even nullifying their own reproductive output. It is less well known that 'brood parasitism' among females of the same species is common in certain fishes, insects and birds. In this conspecific brood parasitism, where females parasitize others of their own species, the host parents will bear a high cost when they feed chicks that are not their own. Ways of reducing these costs are therefore expected to be favoured by natural selection. On page 495 of this issue, Bruce Lyon describes how an aquatic bird, the American coot Fulica americana (Fig. 1), uses several remarkable behavioural tactics to this end. In this species, a parasitic chick that survives usually does so at the cost of a host chick. But the host parents can often identify the eggs of parasites, and reject or otherwise disadvantage many of them.