Pairs of European bee-eaters (Merops apiaster) raise their clamouring families in nest holes dug into sandbanks. When disaster strikes, and an adult loses its eggs or chicks, it seems to do the decent, neighbourly thing, and helps other pairs in the colony to raise their young.
On closer inspection, these apparently altruistic bee-eaters usually turn out to be males that are helping out either their brothers or parents. In this way, the bereaved bird is helping to raise young related to itself, and so ensure the survival of at least some of its own genes.
Being in a position to help one's relatives would seem to depend on related birds nesting reasonably near to each other, as the behaviour would be impractical if birds dispersed so widely between birth and breeding that colonies rarely contained relatives. Females do disperse widely, and that is probably part of the reason why they ...
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