Female birdsong and the sexism baked into science
We tend to picture a singing bird as a male showing off. That picture is mostly a habit, and a fairly recent study of the science behind it suggests the habit was wrong for about a hundred years.
Do female birds sing?
Yes, and far more of them than the textbooks let on. When researchers mapped singing onto the songbird family tree, they found female song in roughly 60 to 70 percent of songbird species. It is not a quirk of a few oddballs. It is closer to the rule.
Better still, the family tree shows that singing was there in both sexes from the start. Female song is the ancestral condition, the setting the earliest songbirds came with. So the females that sing today are not breaking the pattern. They are keeping it. The species where the females have gone quiet are the ones that changed.
That single finding reorders everything. If you assume song is a male invention, the singing female looks like a mystery. Once you know both sexes sang first, the mystery moves: the thing that needs explaining is the silence, not the song. Naomi Langmore and her colleagues lay this out across a body of work running from the late 1990s to now (2021 review).
Why did scientists assume only male birds sing?
Partly because of where they were standing, and because they weren’t looking (classic). Most of the foundational work on birdsong happened in Britain, Europe and North America, the home turf of the universities and the funding and the well-known naturalists. Many of the birds in those regions are migrants, and in migratory species female song really is less common. Field researchers looked at their local birds, saw males doing most of the singing, and treated that as how birds work everywhere (2017 editorial).
It was a local pattern that was jsut assumed to be a universal one. In the tropics, plenty of female birds sing all year, and the researchers based there never found it strange. But the centre of gravity of the discipline sat in the cold north, so the northern version became the official version. The bias about sex and the bias about geography propped each other up.
Was female birdsong really written off as a "hormone imbalance"?
More or less, yes, and the wording in the old literature is worse than the paraphrase. When a female bird was caught singing, the standard explanation was that her song was a "temporary and functionless aberration caused by abnormally high androgen levels." That phrasing comes straight from Langmore's 1998 review of the field.
What we assumed was: a female does something. The something resembles male behaviour. Rather than ask what purpose it might serve for her, the explanation on offer was that she had too much of a male hormone sloshing about and the song was an accident. Aghhhhhh.
We now know female song does plenty of work. Females use it to defend territory, to compete with rival females, to coordinate care of young, and in some species to attract mates. In superb fairy-wrens, for instance, female song looks mainly like a tool for female-to-female competition, and female song rates can track how many chicks a female successfully raises. None of that fits the idea of a meaningless hormonal hiccup.
Did Darwin get female birds wrong?
He set the frame that later got overextended. Song fitted beautifully into Darwin's idea of sexual selection, the showy trait a male evolves to win choosy females, and it became the textbook example. The standard definition that followed described song as long, complex vocalisations produced by males in the breeding season. The word "males" was sitting inside the definition, so female singers were excluded by wording before anyone studied them. A supposedly elegant theory, built mostly from one slice of the world's birds, hardened into a rule that quietly screened out the evidence against it.
What does female birdsong reveal about bias in science?
That "we have never recorded it" and "it does not happen" are different statements, even when decades of literature blur them together. The gap between those two sentences is where a lot of female animals have been losing out.
The clearest illustration is the blue tit, one of the most watched birds in the northern hemisphere and a staple of behavioural research. Despite all that attention, solid evidence that female blue tits sing barely existed until a 2022 study went looking on purpose and found the females singing regularly, with their own structure and contexts. The sound had always been there but (again) they weren’t even looking.
It’s an issue of knowledge and who gets to decide truth (sorry to get all theoretical). But what a field treats as normal often reflects who was doing the watching, where they were, and what they already expected to find. Change any of those and the picture can flip. The female birds were never the exception.
Why this matters beyond birds
Female animals across biology have been studied less, and assumed to be simpler, duller or more passive than the males of their species. Birdsong is one neat, well-documented case of that assumption being measured against reality and coming up short. It is worth keeping in your back pocket the next time someone tells you what females "naturally" do or do not do.
I went much deeper on this, including the texts I fired off to a friend at the time and the bit where I had to correct my own excited theory, in the full essay.
