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There’s a gender gap in ornithology—and this one has nothing to do with equal pay. Instead, it comes down to a lack of love for female birdsong.

Experts have long been curious as to how male birds use their voices to communicate, attract mates, and fend off competition. But they've spent less energy investigating the same behaviors in females. This bias has been ingrained in ornithology since its earliest moments. John James ���Ϲ���, for instance, described male hummingbirds as , and called their mates passive and delicate. Yet he failed to note that female Ruby-throated Hummingbirds : a series of brusque squeaks to warn trespassers away from their nests or food supplies. In contrast, Margaret Morse Nice in great awe and detail.

Decades later, the lack of gender parity is still . “The textbook story is: Male birds sing,” says Katharina Riebel, a professor of biology at Leiden University in the Netherlands, who’s been investigating avian sound for nearly two decades. Scientists have identified close to 660 species with long, complex female vocalizations, she adds—but that’s about where the knowledge ends.

To narrow the gap, there needs to be a shift in how and where studies are conducted, Riebel says. Most avian (and conservation) research in North America and Europe, lending to a skew toward male-only music. For example, out of the 660 known female-singing species, only 120 are based in the Lower 48, Hawaii, and Canada. So this spring, Riebel joined Karan Odom from Leiden University and Mike Webster from the Cornell Lab of Ornithology to launch the , which calls on birders everywhere to seek out members of the unsung sex, specifically from the suborder Oscines (a group that includes familiar songbirds like finches and vireos). They can use any technology—smartphones to recorders—to document and upload sound clips, videos, photographs, and notes to the online database . By dipping into this global pool of volunteers, the trio hopes to gather data from as many different regions as possible, and discover more about the origins and intricacies of female song.

A sonogram of the Magpie-lark's aggressive duet shows the female initiating the song. (Red is female; blue is male). Recording: Courtesy of Michelle Hall

A sonogram of a male-initiated Magpie-lark duet. Both sexes can sing the same tunes. Recording: Courtesy of Michelle Hall

Riebel has always been fascinated by birds' voices, and it's easy to see why. Song is passed down from one generation to the next much in human babies learn to talk from doting adults. Nestlings as they try to absorb and fine-tune the language. It’s an important step in their development; if they can’t communicate later on, they won’t be able to defend territory, woo a mate, or bond with their families and flocks. This, in part, holds true for both sexes. In Australian Magpie-larks, females and males , where they coordinate their songs to scare off other mated pairs. Great Horned Owls , with the female owl typically hooting first.

The tropics are the best place for the project to find new female songs and other tag-teaming species, says Richard Prum, a professor and curator of ornithology at Yale. That's because these areas have the highest amount of bird diversity while also being comparably under-researched. Regions like Southeast Asia and the Amazon River Basin should yield a trove of new, relevant song samples, Prum notes. Many of the species that live along the equator are non-migratory and monogamous, which means they spend a lot of time protecting their territories as pairs. This increases the likelihood that females are more vocal there than in North America. In fact, the tropics are already known to host many accomplished dueters, including African bush-shrikes and Central American wrens, says Kenn Kaufman, ���Ϲ���’s field editor. ​

Map of submissions so far. Courtesy of the Female Birdsong Project

Collecting music from far-flung places, hard-to-ID birds, and unpaid, untrained contributors will take years, maybe decades—but that doesn't concern Reibel. Her goal is to keep engaging and encouraging people until there are thousands of recordings of female song. Even that might not be enough. A broader definition of what constitutes song—one that includes non-Oscine families such as antbirds—would help strengthen the study, Prum says.

As the researchers net additional data, their methods will also evolve. Currently, they’re looking at whether song is absent or present in both sexes of a species; later, they’ll try to tackle the question of how female song evolved. Are the singers concentrated in particular habitats? Do most of them stick around the same home all year? Which groups have the most complex repertoires? The more Ribel knows, the better equipped she is to challenge the ignorance around female birds.

To take part in the project (and in the process, learn how to better ID female birds), .

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