National Geographic News

An adult Houbara bustard (file photo).

Photograph by Adeline Loyau, UFZ/CNRS

Caption: Females that observed highly displaying male birds in the experiment were more fertile and had a greater breeding success due to an increased allocation of testosterone into their eggs, leading to an increase in the growth rate in chicks.Credit: Photo: Adeline Loyau, UFZ/CNRS

A Houbara bustard chick. Photograph by Adeline Loyau, UFZ/CNRS

Ker Than

for National Geographic News

Published June 29, 2010

Watching attractive males strut their stuff makes female birds more fertile and leads to healthier chicks, a new study suggests.

The finding could help improve breeding programs for endangered or threatened birds, because it highlights the importance of mating displays, scientists say.

French researchers studied the mating success of the Houbara bustard, a sandy-colored desert bird found throughout parts of northern Africa and Asia. The species is listed as "vulnerable"—considered to be facing a high risk of extinction in the wild—by the International Union for Conservation of Nature.

When courting females, male Houbara bustards run in circles as they throw back their heads to reveal white throat feathers. Healthier, and thus more attractive, males can run more laps while taking fewer and shorter breaks.

(Related: "Flashier Great Tits Produce Stronger Sperm, Bird Study Shows.")

For the experiment, the team allowed 90 female Houbara bustards to watch other birds before being artificially inseminated. Of that total, 30 females watched healthy-male displays, 30 watched poor-male displays, and 30 saw nondisplaying females.

Females that had watched the healthier males dance laid eggs containing about twice as much of the growth hormone testosterone as the eggs laid by females that watched inferior dances or no dances at all. Testosterone in both genders is associated with building bone density and muscle mass.

(Related: "Women With High Testosterone Take Financial Risks.")

In addition, more of the eggs laid by stimulated females hatched into chicks than those laid by the other two groups.

Sperm quality didn't play a role, because the scientists had randomly selected the vials of semen used for artificial insemination. Even if a female that had watched a high-quality dance was inseminated with low-quality sperm, the resulting eggs had more testosterone.

Seeing Males Can Boost Captive Chicks?

The results suggest that scientists can dramatically improve the quality of bird chicks raised in captivity with a few simple changes to the layouts of breeding centers, said Dirk Schmeller, a biologist at the Station d'Ecologie Experimentale du CNRS in Moulis, France, who was not involved in the study.

"In a lot of cases, females are separated from males, and they never see each other," Schmeller said.

But "if you have one row of females and one row of males, and they could see each other, that could improve the quality of the chicks," he said.

"If these chicks are released into the wild, their probability of survival should be much higher than normally bred [captive] chicks."

Findings were published June 10 in the online edition of the Proceedings of the Royal Society B. The study was conducted by Adeline Loyau, also of the Station d'Ecologie Experimentale du CNRS, and Frederic Lacroix of the Emirates Center for Wildlife Propagation in Morocco.



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