Hatching Asynchrony, Brood Reduction and other Rapidly Reproducing Hypotheses.

Hatching Asynchrony (extended hatching period) is apparently ubiquitous among altricial birds, and may represent a striking example of adaptive family planning. Research has focussed on evaluating various benefits to resulting brood loss. Current conclusions fall into three main categories: that hatching asynchrony is (1) an adaptation to food availability, (2) a means of saving time, ultimately to increase lifetime reproductive success, or (3) a maladaptation. Almost every new study develops a new explanation or qualifies an old one. Either most of them are wrong, or hatching asynchrony is an example of convergent evolution in a behavioural trait serving many functions.