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 focused on evaluating various benefits to resulting partial brood loss. Current conclusions fall into three major 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 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 resulting in a behavioural trait serving many functions.