Asynchronous hatching - Part 2

The third chick hatched this morning. Being 3 days younger than its oldest sibling and 2 days younger than another, it will be greatly disadvantaged. The size disparity is clear to see.


In the wild, the youngest chick from asynchronous hatching being weaker, will not be able to compete with its larger siblings for food during times of food shortage and may starve to death. In this way, the brood size will be reduced when there is a need to balance with the food availability.


However, mother nature can often times be quite contradictory and hard to understand. Studies in some passerines have shown that mother nature will at the same time, also provide the last to hatch with a fair chance to compete with its larger siblings for survival.


Before the eggs are laid, the mother bird, besides the accretion of standard nutrients, will also deposit maternal hormones in the yolk. One of these hormones is testosterone. The eggs will not receive equal amounts of testosterones but instead, the first egg to be laid will receive the least amount and the last to be laid will receive the most. Testosterone plays a compensatory role in the posthatching environment. Studies have shown that elevated yolk testosterone will enhance postnatal growth (e.g. Schwabl 1996; Eising et al. 2001; Navara et al. 2005). This will benefit the survival of later-hatched chicks. Higher yolk testosterone is also hypothesized to enhance posthatching begging, further benefiting the later-hatched chicks.


In captivity, free-flow food supply will be provided and there will be no exception for this clutch. Hopefully, this last-hatched chick will soon catch up with its older siblings.