WASHINGTON- It pays to have a well-dressed dad. Scientists studying how some female birds vary the hormones in their eggs have discovered that zebra finches give a boost to eggs fertilized by males that are, ineffect, better dressed.
The researchers in France and Scotland found that the females included more testosterone in eggs fertilized by some males and less in those from other fathers, depending on what color leg bands the researchers had placed on the males.
The ladies preferred red. "But of course, in the field, male finches do not wear rings," lead researcher Diego Gil of the University of Paris pointed out.
"What they do have is red beaks, which are used by females to choose mates. What seems to happen is that by using rings in the lab, we have tapped into a female-perceptive mechanism, and the female sees the red-banded male as a supermale," he said.
Previous studies have indicated that,in canaries at least, chicks hatched from higher testosterone eggs are more aggressive and more effective at begging for food and grow faster than other chicks.
The new findings, reported in a paper in today’s edition of the journal Science, raise questions about the longstanding assumption that, in birds, the offspring of more attractive parents do better simply because they inherit good genes from their more-attractive fathers.
It is not something the female thinks about, thought.
"To assume consciousness on the part of the female would be a big leap," Gill cautioned. "We consider the differential investment as a physiological reaction."
Professor Hubert Schwabl of Washington State University, who first discovered that some female birds can vary the hormones in their eggs, termed the finding "exciting."
"The surprising result is the influence of male attractiveness on these hormone levels," said Schwabl, who was not part of the research team.
"The conclusion one has to make here is that, when you think about female choice in mate selection, it might not be just getting good genes," he said. "It's something from the females, too".
The researcher found that, given a choice, female zebra finches have a thing for males with red leg bands, but turn up their beaks at those wearing green.
Twelve females were randomly assigned either a green or red-banded male and allowed to produce a clutch of eggs. They were then switched to a male with the opposite color band and produced another clutch of eggs.
"Females mated with red-banded males deposited significantly more (testosterone) in the eggs then did the same females when mated to green-banded males," reported the team.
Douglas Mock of the University of Oklahoma said the work "pulls the rug out" of the assumption that the female is just looking for good genes in more-attractive males. "The female still has another vote to cast."
"You take the same guy, you change his clothes, and the female reacts differently," he added. "It's very elegant."
© lady gouldian finch.com 2016