Many birds hatch their eggs asynchronously while other species are more synchronous.
An extreme food shortage in a Lesser Black-backed Gull colony allowed us to examine the timing of mortality of nestlings relative to sex and to hatching order. This was carried out in experimentally-created synchronous and asynchronous broods, where the latter mimicked the normal hatching spread. Unambiguous sexing was facilitated by use of molecular methods. There was no difference in survival time of the sexes in synchronous broods. This suggests that chick sex-ratio is, at least partly, a function of asynchrony.