Hatching asynchrony can have long-term consequences for offspring fitness in zebra finches under captive conditions

Hatching asynchrony can have profound short-term consequences for offspring, although the long-term consequences are less well understood. The purpose of this study was to examine the long-term consequences of hatching asynchrony for offspring fitness in birds. Specifically, we aimed to test the hypothesis that hatching asynchrony increases the sexual attractiveness and fecundity, respectively, of early-hatched male and female zebra finch, Taeniopygia guttata (Vieillot, 1817) offspring. Mate-choice trials comparing male nestlings with the same parents, but that were reared in asynchronous or experimentally synchronous broods, revealed no female preference in relation to hatching regime. We did however find strong evidence that, as adults, late-hatched males were more attractive to females than siblings that had hatched earlier. Meanwhile, we found a weak trend towards early-hatched females depositing more carotenoids and retinol in the egg yolk than late-hatched or synchronously hatched females, although there were no differences in terms of clutch characteristics or the deposition of α-tocopherol or γ-tocopherol in the egg yolk. Therefore, we found that the beneficial long-term consequences of hatching asynchrony were sex specific, being accrued by late-hatched male nestlings and by early-hatched female nestlings. Consequently, we conclude that the long-term consequences of hatching asynchrony are more complex than previously realised.