Wild Life
08.02.2023

Call of the Liar

The notion that only male birds sing has long been assumed. But evidence increasingly shows that females do, too. Now, scientists are studying a sensational singer in Australia to suss out why.

Down in a gully, beneath a canopy of tree ferns and towering mountain ash, I hear the echoing clacks and undulating whistles I’ve been searching for. It’s taken a leech bite, a few thwacks to the face by branches, and a plunge into shin-deep mud on this crisp day in late May, but at last ecologist Alex Maisey has guided me to his home’s greatest attraction: the superb lyrebird.

The creature is brown and pheasant-sized and nearly lost in a sea of green, save for that it sings and dances atop a scratched-up mound of dirt. I can tell by its lyre-shaped plume that it’s a male. His shivering silver and brown tail feathers spread and fold over his face, almost like a human hand cups to share a secret. But this is no whisper. If a female were on the mound, he’d be screaming at her. As I watch through binoculars, Maisey translates the bird’s best impressions: “Grey butcherbird. Crimson rosella. Golden whistler. Magpie.” I recognize the roll of kookaburra laughter. My jaw drops when the bird mimics the whooshing sound of wings.

Superb lyrebirds, Menura novaehollandiae, are world famous for their near-perfect imitations. Human admirers come from far and wide to hear them here in Sherbrooke Forest, just outside of Melbourne, Australia, on the custodial lands of the Wurundjeri people. Each winter for more than 60 years, local enthusiasts like Maisey have hiked through the forest at dawn to keep tabs on the lyrebirds. One man from Melbourne was so obsessed with observing the species that he opted to live part-time in the forest within a massive hollowed-out log.

Of particular interest are male lyrebirds, who not only look showier but act that way, too. They have several different songs. One is a series of whistles, whoops, wails, and warbles that, aside from a few bouts of embedded mimicry, is unique to the species. Other songs are used to court females and include up to 80 percent mimicry. Lyrebirds can copy the sounds of more than 20 other species as well as the clack of beaks and the squeak of rubbing branches. They can even sing two overlapping bird songs at once.

Their outlandish performance is a classic example of an excessively complex trait or behavior that was likely shaped through “sexual selection.” Charles Darwin first introduced this theory in 1859 to explain why elaborate, seemingly non-adaptive characteristics, such as a peacock’s tail, persist over generations. Virtually all birds make short calls to communicate. But according to Darwin, birdsong, which is more lyrical and complex, belongs almost exclusively to males, who use it to either attract mates or establish territory; the role of females is to silently judge whose melody is most appealing.

What started as a revolutionary idea in biology has, in the time since, closed many scientists’ ears to competing narratives. Indeed, when biologist Anastasia Dalziell first started studying lyrebird songs in the late 2000s, she only focused on males as only male lyrebirds enjoyed a reputation for mimicry. Shortly after finishing her doctorate on lyrebird mimicry, however, the musician-turned-ornithologist realized her thesis needed revision. During a stint of fieldwork in the Blue Mountains, a forested landscape of peaks and valleys west of Sydney, Dalziell kept hearing female lyrebirds singing and mimicking.

People who live near lyrebirds had also heard females vocalize, especially when someone approached a nest. But no researcher had formally documented these instances in the scientific literature. Historically, scientists have dismissed female song as exceptional, inferior, or functionless—an accident of sexual selection. In 2014, however, a global survey of songbirds revealed that lyrebirds are far from alone in their abilities: Females sing in a whopping 71 percent of species examined. Compared to other regions, females in Australia—where songbirds first evolved—are particularly vocal. And the lyrebird lineage is the oldest of them all, with fossils dating back more than 15 million years.

Eager to hear some of the most time-honored female voices in the world, Dalziell, together with Justin Welbergen, set up a dedicated line of research as part of their program called “Lyrebird Lab”. Ecologist Vicky Austin of Western Sydney University has led the ear-opening endeavor. Her findings suggest that female lyrebirds are just as skilled at singing as males, though they do so for different reasons. In the Blue Mountains, Austin has shown that females consistently whistle their own tunes, interlaced with imitations of other birds.

Her experiments in the wild are the first to suggest that lyrebirds use mimicry to protect the nest. For example, when a lyrebird mother feels threatened by a pied currawong, an egg eater with leering yellow eyes, she will often imitate the calls of larger predators, possibly to frighten or confuse, and draw the burglar away from the nest.

“We’ve only just unraveled the fact that female birds sing, but there’s this whole other section now about mimicry that we’re trying to get to the bottom of as well,” Austin says. “If females aren’t using mimicry to attract mates, then how does it evolve?”

For thousands of years, superb lyrebirds have drawn a human audience. Some Indigenous Australians know the bird as beleck-beleck or balangara and many describe it in their Dreamtime stories as the peaceful broker of the bush—the only animal able to communicate with all others. The first colonial settlers found the lyrebird’s song disturbing and unnecessarily hunted males for their tail feathers, which fall out each year and can simply be picked off the forest floor. It took more than a century for the species’ tune to become a cherished anthem for the new nation. In 1931, a male lyrebird from Sherbrooke was the first wild bird broadcast on Australian radio.

Even before recording sound was possible, tales of the lyrebird’s song drew the attention of John Gould, the so-called father of Australian ornithology, as well as the first scientists to formally describe evolution, Alfred Russell Wallace and, of course, Darwin. None of these English naturalists could ultimately agree on why the lyrebird sang or mimicked to such excess. Gould did not accept the theory of natural selection, and Wallace thought a female must choose a trait or behavior because it offered some concrete survival advantage to her offspring, not because she found it aesthetically appealing.

But where Wallace found the male lyrebird “most conspicuous” and “wonderful,” he described the female merely as “unadorned.” Similar perspectives riddle scientific literature. In 1900, Australian-born naturalist Archibald James Campbell wrote, for example, “that only the cock bird whistles and mocks in this magnificent style; the hen makes but feeble attempts.” Darwin, for his part, also hewed to the idea of male superiority. He used lyrebirds to illustrate the central idea of his seminal book, The Descent of Man, and Selection in Relation to Sex, which explores the struggle between males of various species “for possession of the females.”

Pretty much ever since, feminist evolutionists, sometimes called Darwinian feminists, have been working on a more inclusive theory that doesn’t assume males are naturally “superior.” “Social selection theory,” is one way to level the playing field. Popularized by the biologist Mary Jane West-Eberhard in 1978, the theory has come to frame all animal interactions as forces that can shape species, not just those among potential mates or between males. In both sexes, the theory goes, competition and cooperation for food, territory, nesting sites, and other essential resources can contribute to the development of elaborate traits.

It was a duet that initially inspired ornithologists to take another look at the social context of female song. When barred owls (Strix varia) court, the male and female trade a series of alternating gurgles, hoots, caws, and cackles that echo through the treetops like a troop of noisy monkeys. A behavioral ecologist named Karan Odom studied the duet in the late 2000s and began to wonder: If each sex has their own distinct part, could females of other species be singing too?

For more than a century, Western science had defined birdsong as the longer, lyrical, and more elaborate vocalizations that male birds make during the breeding season. But what if that definition was too narrow? Odom joined with other like-minded scientists to look back in history and see if females were ever heard vocalizing in complex ways, even if, at the time, that wasn’t technically considered singing. She spent months pouring through 16 large tomes detailing every described bird species. “I was really surprised how much female song was documented, how much it seems to crop up, again and again,” Odom, an author of the 2014 survey, tells me. Across the songbird tree, female voices were clamoring to be heard. Odom and others went on to create the Female Bird Song Project, an online database that aims to systematically catalog female birdsong globally.

“Males are pretty; they’re loud; they’re obnoxious; they’re just in your face…. I get it, but it’s the subtlety of females that interests me. You have to be patient.”

— Vicky Austin, Western Sydney University

Down Under, researchers at the Lyrebird Lab are doing their part. Austin, Dalziell, and Welbergen are the first to place cameras and microphones in and around lyrebird nests. “It’s not all about the males. Rights for females!” Austin half-jokes, pumping an imaginary protest sign as we scramble through wet forest, across streams, over boulders, and under fallen trees on a rainy day in September. We are hunting for female lyrebirds in the Blue Mountains, on the traditional lands of the Dharug and Gundungurra peoples. Suddenly, I hear a high-pitched whip-crack echo through the blue gums, closely followed by a double note: Cooooowheep! Pew! Pew! Austin identifies the sounds as a male and a female whipbird (Psophodes olivaceu). The coordination of their duet was so finely tuned, that if I assumed males were the only singers, I’d have never heard the female’s voice.

Austin keeps her ears peeled but she guides us mainly with her eyes, surveying the forest floor for signs that a lyrebird has been scratching. With young to protect, females rely on silence and subterfuge while they forage for insects or build their nests. Finding them requires dedication and, like today, many unsuccessful outings. It took Austin months to be able to tell the difference between a lyrebird mimicking a goshawk and an actual goshawk—and that distinction is based more on location and behavior than on any noticeable difference between the calls themselves.

“Look,” Austin tells me matter-of-factly when I ask why female song has been disregarded for so long, “a big part of it is that males capture our attention. Males are pretty; they’re loud; they’re obnoxious; they’re just in your face. They’re beautiful, and I get it, but it’s the subtlety of females that interests me. You have to be patient.”

Austin’s years of persistence have paid off. Dressed in camouflage, she’s spent hours crouched outside lyrebird nests, waiting to hear their morning whistles.

Sometimes, she’s noticed, they also sing while foraging. Similar to male lyrebirds, the female’s whistle song is embedded with bouts of mimicry, although their imitations are not as repetitive and they tend to copy more predators. The reasons for the whistling are unclear, but Austin suspects it involves competition for space and resources—and the ongoing need to signal one’s presence to defend those assets. Female lyrebirds are aggressive with one another, destroying each others’ nests and attacking each others’ young. Mothers often build multiple nests throughout their territory, possibly as back-ups, decoys, or territorial markers. Whistling a song every morning could be a safe and easy way to signal: No trespassing.

In one set of experiments, Austin challenged wild female lyrebirds as they left their nests, pulling back a sheet to reveal a stuffed fox, currawong, or rosella. Each of these taxidermied intruders triggers a different response from lyrebirds. Females mostly ignore the innocuous rosella, a colorful parrot that poses no threat to lyrebirds or their offspring. But when a fox is present, females scream in a way that implies multiple voices, like an army of birds facing a threat. Lyrebirds might produce this disorienting alarm to fool a predator into thinking it’s outnumbered or to recruit other animals to drive the threat away.

Once, Austin observed a mother respond to a currawong at her nest by calling in an ear-splitting mob of bell miners, a native species of honeyeater that swarms and chases native birds from food sources. Another of Austin’s recordings shows a female lyrebird flapping and singing around a goshawk perched at her nest entrance. Three-quarters of her cries involve mimicry, mostly of smaller birds such as scrubwrens, king parrots, and whipbirds. More detailed research needs to be done, but Austin is convinced that mimicry “isn’t just a pretty thing. The female is actually using it functionally.

And why not? The stakes are high and lyrebird defenses are limited. Each year the female lays just one egg. This chick takes six weeks to hatch and another month to leave the nest, which is unusually slow for a bird. Meanwhile, males don’t care for offspring at all, leaving females responsible for the species’ survival. “We’ve now got to consider that, in fact, mimicry was all about anti-predator function or about nests,” Dalziell explains. “And then it got co-opted into a sexual signal.”

Most research on vocal mimicry to date has focused only on males, but the few studies that involve both sexes suggest mimicry is used for more than just courtship. In 2017, researchers in the United Kingdom recorded common cuckoos (Cuculus canorus) imitating predatory sparrowhawks to scare other birds off of their nests. The cuckoos then snuck their own eggs into the mix and escaped parenting duties. In 2021, another team in China caught female great tits (Parus major) hissing like snakes when squirrels threatened their nests. In South Africa scientists recently documented fork-tailed drongos (Dicrurus adsimilis) mimicking meerkat calls that communicate a nearby threat. After the meerkats fled, the drongos stole their food.

Other times, it’s not clear why birds imitate the sounds of other species. Scientists in North America recently discovered that female northern mockingbirds (Mimus polyglottos) also mimic like their famous male counterparts. Ornithologist Christine Stracey was placing cameras in and around mockingbird nests to study their reproductive behavior when she noticed an audio feature on the device. She flipped the switch and opened her ears to a whole new world of bird sounds. Stracey shared her recordings with Dave Gammon, a biologist who has studied the species for more than a decade. Sure enough, he confirmed the females were imitating other species.

Male mockingbirds mimic to court and define territory. But researchers have yet to discover why females are mimicking. Initial findings suggest that female mockingbirds might even expose their nest to predators when they vocalize. So why do it? Gammon thinks it could be a byproduct of the species’ innate song-learning abilities. Stealing other songs could be an easy way to expand a repertoire, or it could even be a form of play. “I think of [mimicry] as part of the package that got dragged along with [song],” Gammon tells me.

Even without a clear purpose, it’s possible that an extreme trait like mimicry can persist through generations, via genes or the way a brain is wired—as long as it’s not significantly detrimental. In other cases it really might be about beauty. As evolutionary biologist Richard Prum has pointed out, sexual selection isn’t just about male prowess. It also posits that females powerfully sculpt the evolution of their species simply by choosing mates—what Prum calls “Darwin’s really dangerous idea.” Elaborate behaviors like mimicry don’t have to be useful to exist, Prum says; they could be “merely attractive.”

The idea that mimicry can have multiple origins is supported by hard data. Unlike birdsong, which appears to have arisen in a common ancestor and spread widely through the songbird tree, genetic studies suggest vocal mimicry evolved independently on 237 separate occasions and then disappeared in at least 52 of those cases.

Even within the same species, the use of mimicry is highly variable. For male lyrebirds, learning to vocalize seems to be open-ended, meaning that they continue to accrue and improve their repertoire throughout life. That’s probably what allows them to mimic fire alarms and crying babies when housed at a zoo. But among females, initial studies suggest the best mimics are not necessarily the oldest. Alex Maisey tells me that one young lyrebird in Sherbrooke was so vocal, she was known to locals as the “singing female.”

Compared to those in the Blue Mountains, most female lyrebirds in Sherbrooke do not sing consistently. Maisey has spent many a morning huddling near nests in the predawn to confirm what Austin was hearing a state away—but he was met with silence. Perhaps in a smaller forest, where lyrebirds and their predators are more concentrated, singing near the nest is simply too dangerous. When a chick is around, Austin says even females in the Blue Mountains are quieter than normal, most likely for fear of giving away their presence to predators.

In such moments of silence, it’s worth remembering: If a female bird isn’t singing, it doesn’t mean she can’t.

The easiest female lyrebirds to find in the Blue Mountains nest near the busy boardwalks of a place called Scenic World, a former coal mine at the base of a sheer sandstone cliff that’s now a tourist attraction. To reach the forested valley, Austin and I ride the world’s steepest passenger railway. We have just stepped off an established path when she holds up a finger. “Do you hear that?” It’s a note of goshawk. I look down to see a brown bird with a small, sleek head, reddish wings, and a bent tail, its spindly leg frozen midway through pulling up a root. “They look like dinosaurs,” laughs Austin, as the bird dashes behind a tree. We sit and watch the female forage, the quiet broken only by the occasional trail runner shouting a cheery g’day, oblivious to the bird in the bush. 

Austin calls this lyrebird Diana. Her ears are now so tuned to females, she can identify individuals by voice alone and can discriminate between regional “accents.” “This is how we discover things,” Austin says, “It’s just humans being interested in the world around them.”

By the look of Diana’s tail, she’s been cooped up in her nest for weeks. In Austin’s time knowing her, she has raised two chicks to maturity, which apparently is “pretty good.” One year, though, a tabby cat—likely from a neighborhood up on the cliffs—stole Diana’s chick a day before it was due to fledge. But lyrebird mothers, perhaps, don’t take losses like that lying down. “There are a couple of female lyrebirds, one here and one in the gully just over, that mimic cats,” Austin says. She’s never heard a male meow, but she’s never searched for it, either.

This story was published with grant support from the Science Journalists Association of Australia.

Carly Cassella

Lauren Owens Lambert

Carly Cassella is an independent science journalist who writes about the natural world and our place within it. Her work has been published in The Atlantic, Australian Geographic, High Country News, and more.

 

 

 

Meghan Lindsay

Radim Schreiber

Meghan Lindsay is a nature photographer and writer based in Australia. She is passionate about sharing conservation, scientific, and other environmental stories through her images, videos, and words.

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