In one of the stranger expressions of gender inequality, female birdsong has been largely ignored by ornithologists, researchers claim.
The image of a brightly coloured male bird singing furiously to proclaim his breeding territory, while a dull-coloured female silently tends to the nest is simply not applicable to most of the world’s birds. Indeed, a 2016 survey of singing behaviour in all songbirds found that females sing in 64% of species in which the male sings.
And yet female birdsong is critically underrepresented in both the scientific literature and in biological sound recordings. A new paper in the journal The Auk: Ornithological Advances argues that a better understanding of these unappreciated songs could lead to advances in many aspects of bird biology.
Authors Karan Odom of Cornell University and Lauryn Benedict of the University of Northern Colorado, both in the US, became intrigued by female birdsong through their own research.
“I started studying California towhees 17 years ago, and I was fascinated by the duet vocalisation given by females and males,” explains Benedict.
“That led me to start looking for female song in other North American bird species, and I was surprised to learn that it was much more common than I expected. The reports of female song are buried in odd corners of the literature, but when you put them all together, you start to see some interesting patterns.”
The bias came about because most studies of birdsong have come from temperate regions of the world such as North America and Europe, where male birdsong is used to proclaim breeding territories after arrival from their wintering grounds. Even in temperate regions, however, a closer look at female song behaviour reveals that some 42% of resident songbird species have females which sing.
Odom and Benedict believe that the study of female song is essential to further our understanding of birds’ comparative physiology, neurobiology, behavioural ecology, and evolution – in fact, everything we study about birds.
In Australia, the superb lyrebird (Menura novaehollandiae) presents a classic case of the male of the species overshadowing the female, to the detriment of our understanding of the species’ behavioural ecology. The male is heavily decorated with elaborate plumes in his lyre-shaped tail, and he performs spectacular songs of mimicry on a carefully created stage.
The bird has been studied extensively for centuries, but it took until 2016 for researchers to publish a study on the song of the female lyrebird – which also turns out to be an accomplished mimic.
The authors, Anastasia Dalziel from Cornell University, and Justin Welbergen from Western Sydney University in Australia, believe that their study throws out “previous portrayals of vocalisations by female lyrebirds as rare, functionless by-products of sexual selection on males”. Instead, the research suggests that their song plays a role in nest defence and female-female competition for breeding territories.
There is another, more pragmatic, reason to take note of female birdsong – if ecologists are surveying a threatened bird species, then a mistaken assumption that all singers are male could result in an inaccurate picture of population size.
Odom has created an online platform to encourage scientific research, naturalist notes and recordings of female birds, and above all to raise awareness that female birds do indeed sing.
“If you hear a bird singing, do not assume it’s a male,” Odom says. “If you observe a female bird singing, document it by uploading field notes, audio, or video to the collections on our website. Make sure to indicate how you recognized the bird was female.”
For Australian birders, it is worth noting that many of the species listed on Odom’s website are widespread and oft-encountered birds such as spotted pardalote, rufous whistler, scarlet robin, satin flycatcher and olive-backed oriole. In fact, eight out of the 10 families listed on the website where very little is known about female song are endemic to Australia.