Singing duet may help this bird couple to stay together

US researchers have identified a peculiar behaviour of singing duet in Red-backed Fairywrens, a promiscuous bird specie found in Australia, to keep up with a mate.

The scientists discovered a queer habit of crooning duets in the fairywrens when they notice an intruder. The male and female will immediately fly together and perch on a branch right next to each other and start belting out duets.

Those who reacted quickly and sang duets more are said to have a "strong" duet-singing response. Others were slower on the uptake.

"We found that pairs with a strong duet response had lower rates of cuckoldry," said study author Emma Greig, scientist at Cornell Lab of Ornithology in US.

The pair with a strong duet response were also found less likely to mate outside of their pair bond when they sang together more, the researchers explained.

"If the males are particularly riled up, they will do this 'puff-back' display, raising the orange or red feathers on their back to the intruder. While singing duets, their heads are thrown back to the sky with their beaks wide open," pointed out one of the researchers, Daniel Baldassarre.

Even when pairs have a strong duet response, sometimes the mates still stray, but it does increase the likelihood that they're raising mostly their own genetic offspring.

The results of the study published in the journal Biology Letters suggested that the females decide what males to cuckold. Male Fairywrens, whether aggressive or not, are often cuckolded by the females.

"Our results suggest the females are deciding what males to cuckold. Females are either being influenced by their mate's songs, or females are indicating their own choice by singing with their mates more. We need more detailed work to distinguish these alternatives," Greig added.

Famous for their legendary courtship and mating behaviours, the Fairywrens are known to be among the least faithful birds in the world, with an extra-pair mating commonplace, resulting in eggs often fathered by various different birds.