Male birds in poor physical condition may cheat unknown females and give a false impression by faking their song, suggests a new study.

Researchers from Université de Bourgogne in France and University of Exeter in the United Kingdom studied zebra finch birds, in order to find out how their songs help in providing honest signals about the male's value as a mate.

For their study, the research team looked at 91 male and 91 female birds from a colony at the Université de Bourgogne and 12 of each gender from a colony at the University of Exeter. They videoed long and short encounters of male birds with unknown females as well as their song patterns when familiar female birds were around.

Birdsong plays a significant role in attracting females. The research team found that healthy male zebra finches sang songs at a higher rate than birds in poor physical condition.

They did not notice any difference in the songs sung by male single birds in either long or short encounters with strange females.

But, they found that some male birds in poor condition cheated unknown females by changing their song so as to show themselves in good physical condition. However, these unhealthy birds refrained from deceiving their long-term partners, as the females can easily judge the real condition of the male on hearing his song.

"Every man wants to cast himself in a favourable light when he meets an attractive female, and we have shown that birds are no different. But just like many humans, it seems zebra finch males are unable to dupe females who know them well enough. When the birds were in an established relationship, the female could tell the true condition of a male by his song, and judge whether he would make a good father for her next brood," study author Sasha Dall, of the University of Exeter, U.K., said in a statement.

This is the first study showing a link between male body condition and birdsongs, said Dr. Morgan David, lead author of the study.

According to David, the study could help in understanding more about the evolution of courtship patterns such as birdsongs.