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Birds who choose their own mate have more babies, says study


A new study has revealed that birds that choose their own mates have more offspring than those that are paired up by researchers in conservation and captive breeding practices, the guardian reports.

According to the study, birds that freely choose produce 37 percent more offspring than those that were paired up.

The study was published in the peer-reviewed journal, PLOS Biology. 

The experiments also revealed that embryo mortality was dependent on the compatibility of the genetic parents, whereas chick mortality depended upon the behavioural compatibility of the foster parents.

So, even though parents that freely chose their own mates had similar rates of embryo mortality to those who didn't, those birds that freely chose their own mates were much better at raising their chicks. Therefore, it implied that birds might be choosing mates based on behavioural compatibility.

The benefits of mate choice range from resources like food or territory to the "good genes" that increase offspring survival.

"For example, female frogs almost always chose males with deeper voices, and female birds usually prefer males with brighter plumage or longer tails. These male traits are assumed to signal benefits to females, which is why females prefer males with more extreme expression of these traits", said behavioural ecologist Michael Jennions, a professor at the Australian National University, who was not part of this study, according to the guardian.

 "[T]here has been strong interest in showing that a major benefit of this type of mate choice is genetic", explained Professor Jennions in email. "[B]y mating with preferred males, females elevate the fitness of their offspring because these male traits signal heritable genetic quality."

Behavioural ecologist Malika Ihle, a PhD from the Max Planck Institute for Ornithology, worked under the mentorship of her supervisors, to conduct a study to identify the benefits of mate choice due to partner compatibility and to separate the indirect advantages of compatibility from the direct ones.

Dr Ihle and her colleagues studied a captive flock of 160 bachelor zebra finches, Taeniopygia guttata.

After a series of experiments, the study concluded that birds display idiosyncratic tastes in choosing their mates. This compatibility causes the females to increase the likelihood of successful copulation and encourages better raising of the chicks.

 "Embryo mortality (which is presumably driven by genetic compatibility) did not differ between eggs of females assigned their chosen male or another male (regardless of who was looking after the eggs). This suggests that the idiosyncratic mate choice of females is not driven by genetic benefits for offspring (at least for any that act early in life)", said Professor Jennions.

"In contrast, offspring reared by a female paired with her chosen mate, rather than with another male, had above average survival (regardless of whether or not the pair were the parents of the offspring they reared)", said Professor Jennions.

"This suggests that females are choosing males based on their social compatibility as partners that work well together during child rearing", said Professor Jennions.

The results of this study are consistent with studies based on the differences between love-based and arranged marriages in humans.

"In humans, some studies suggest that individuals are more satisfied, more committed, and less likely to engage in domestic violence, when involved in a love-based rather than an arranged marriage", write the authors in their paper.

Tags birds, love
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