According to experts, the study demonstrates a strong gender selection based solely on the looks of the mate. A female Gouldian finch can control the sex of her chicks in response to whether her mate has a red or black head. If there is a mismatch she produces more males and is not attentive towards her offspring.
Sarah Pryke, a biologist and lead author of the study from Macquarie University, said the discovery would change the perception of sex determination across the animal kingdom.
She said, ''It really suggests that females have a lot more control than we ever gave them credit for. It's kind of amazing to think about because birds have a sex chromosome determination system like we humans have.”
Pryke and a team of researchers investigated sex determination in the two most common morphs of Gouldian finch, red and black. They took 100 red-headed and 100 black-headed female birds and mated each of them twice with a male of the same head color and a male with the different head color. They found that color coordination in couples produced a balanced sex ratio, with 45.9 percent males, where as mismatched pairs produced broods that were 82 percent male.
To decipher whether the reason was because of a chemical or genetic interaction between the birds, Pryke and the team then set about tricking the female birds by deliberately dyeing red males’ head a shade of black.
The mating of red females and pseudo-black males produced more males (72 percent males) despite being genetically compatible. When black females mated with a bird of the same head color, even if that color was artificial, the ratio was even (55 percent males).
Another thing observed was that when the colors matched, the mother produced more eggs and was more attentive in feeding and caring for her offspring. However, it was noticed that daughters still eventually died when the parents were mismatched, than when the parents shared a similar colored head.
Sarah Pryke said, “It is pretty amazing to think that the female herself has so much control - subconsciously of course - over this basic physiology.”
She stated that the exact mechanism by which females determine their offspring’s sex “is a big mystery”, but one possibility could be that perhaps a different colored head raises female stress levels, producing hormones disrupting the routine processes of fertilization.
Scott Ramsay, an ornithologist at Wilfrid Laurier University in Ontario, Canada said that the findings "illustrate a level of maternal control [over offspring gender] ... that I don't think has ever been demonstrated."
The study is published in the journal Science.
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