The chore of raising young chicks is one some birds manage to avoid. By laying their eggs in the nests of others, they dupe those others into feeding the babies once hatched. Such ‘brood parasitism’ has been noted in at least three groups, namely cuckoos, cowbirds and honeyguides. It provides a good example of convergent evolution, in which unrelated groups with similar ways of life evolve similar adaptations that help them thrive. The adaptation noted in these three groups of birds is that the shells of their eggs are significantly thicker than those of the birds they parasitise. To demonstrate that this is an example of convergent evolution, a benefit has to be shown to be associated with the adaptation. In this case, the thicker shells have been shown to provide greater warmth, enabling the parasitic chicks to hatch sooner than the chicks of the host bird – giving a greater chance of survival.