In a nurture-over-nature twist, scientists studying zebra finches found that a mother's investment in early eggs has a greater effect on her son’s good looks than what papa finch actually looked like.
Zebra Finches are charmers. The males in particular know how to impress a lady: each has a unique song and irresistibly cheery orange cheeks.
As in many bird species, babies in the same nest don’t share the same biological father. Though males and females pair to raise young, both have their fair share of amorous encounters with other birds.
The long-held theory has been that mama finch occasionally falls for a feathered Don Juan and these liaisons allow her to mate with handsome males and boost the genetic quality of her brood (like father, like son). However, as the University of Zurich’s press release details, children of these trysts don’t necessarily owe their looks to dad.
Instead, scientists found that earlier-laid eggs get a greater share of maternal resources and that leads to more attractive, healthy finch sons. Specifically, the first few eggs are larger and more nutrient-packed than later lays.
Unfair favoritism? Hatchlings of early eggs are more likely to survive and succeed, so mother’s extra investment may reflect the tough realities of survival.
You can find the aptly-titled paper, "When mothers make sons sexy..." on the Proceedings of the Royal Society B website.