Why are We Having More Aggressive Female Birds?

Khryss | Published 2017-11-15 05:06

They seem to be stopping their silence and now sing like males.

Female dark-eyed juncos (Junco hyemalis) occasionally sang in captivity when injected with testosterone, said Dustin Reichard of Ohio Wesleyan University. However, he wanted to know if they also sing when free in the wild and without alterations done.

So, together with his colleagues, they've provoked them by putting a live, caged female inside their territories. To add up, they've also played recordings of a soft quaver that usually signals the females' readiness to mating.

17 females and 25 males have appeared to interact with the caged females. To the researchers' surprise, while half the females dived and lunged at the caged ones, some of them had shown those aggressive tail-spreads! Three of them even managed to sang songs like males. The two latter behaviors are not actually normally seen in females.

“The context in which the songs were observed – responding to a female intruder – suggests these songs have an aggressive, territorial function,” says Reichard. “But we can’t say whether female song is specific to female intruders without also measuring their response to male intruders.”

They also didn't seem to be happy about males' attempts to court the caged female. These species are monogamous and females try really hard to keep their mates faithful.

“The results provide some of the first evidence that female song can be rapidly regained in a songbird species,” says Jordan Price at St Mary’s College of Maryland, who has documented female songs in New World blackbirds. This is greatly due to a shift in their lifestyle.

“The junco population we studied actually stopped migrating about 35 years ago and became year-round residents of San Diego, California,” says Reichard. “It may suggest that if a species loses its migratory lifestyle, they might gain female song [to defend territories],” he says.

“Recent studies are showing that female singing is much more common than previously thought, especially in birds that are non-migratory and in which males and females defend territories all year round,” says Price. “But in temperate-zone songbirds, the widespread belief is that males sing and females don’t.”


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