Female European robins (Erithacus rubecula) sing throughout autumn and winter 鈥� and their songs are just as physically and mentally challenging as those of males.
Outside the breeding season, when food and hiding places are scarce, both sexes sing equally difficult songs to mark the limits of their individual territories. The finding discredits the popular belief that only male songbirds sing, as well as any assumptions that they would sing better than females, says at the University of Paris Nanterre in France.
鈥淥ne of the motivations behind this study was to get females heard in studies on bird songs because, for a long time, researchers were focusing only on males and thought that whenever a bird was singing, it must be a male,鈥� she says.
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Until the 21st century, scientists generally believed that the primary purpose of bird songs was for males to attract females, says Geberzahn. Recently, however, , and they even found evidence suggesting that the earliest bird songs might have evolved in females as well as males.
Increasing diversity among researchers may be one reason behind the change in perspective: another study found that , but less likely to be the first author of papers about birdsong in general.
鈥淲e used to think we had to find a way to explain why [singing] evolved in males, but not in females,鈥� says Geberzahn. 鈥淏ut it鈥檚 probably more accurate to ask, why has it disappeared in some species in females?鈥�
快猫短视频s have also questioned whether the quality of the songs differs between males and females, she says. To investigate, Geberzahn and her colleagues recorded the regular territory-marking songs of 22 European robins, half of which were female, from October to December. The birds lived and sang freely on the wooded campus of the University of Paris-Saclay and were captured just long enough to be fitted with identification rings, measured and sexed through blood sampling, since they look so similar.
The researchers analysed an average of nearly 12 songs per bird, all sung spontaneously 鈥� meaning they weren鈥檛 responding aggressively to another bird approaching their territory.
Both males and females produced very complex spontaneous songs with multiple variations and frequencies ranging from 1.5 to 12 kilohertz 鈥� all within the human hearing range, she says. They had the same kinds of frequency variation, with similar extremes and switches within comparable gaps of time. And they took essentially the same kinds of 鈥渕ini-breaths鈥� within their songs.
The researchers used this information to calculate a vocal performance score for each bird. Male and female robins had similar scores, showing their songs had similar muscular, neurological and respiratory demands.
The findings make sense, especially in a species that lives alone half the year, says Geberzahn. 鈥淏oth males and females need to be equally capable of defending their territory against other males and females,鈥� she says.
To their surprise, however, the scientists found that the birds鈥� vocal performance wasn鈥檛 related to their weight or to their wingspan 鈥� contrary to theories that songs should provide an 鈥渉onest鈥� reflection of the singer鈥檚 body condition. That could be because the songs were just spontaneous, Geberzahn says. Songs sung in reaction to a threat from another bird might better reflect the singer鈥檚 size 鈥� a topic her team hopes to investigate in the future.
Animal Behaviour
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