Female Birds Finally Get Their Due

Gender bias isn’t limited to humans. Long overlooked and understudied, female birds are receiving more attention, with implications for their survival.

By Laura Tangley
Science News
Mar 28, 2024

In many birds, from eastern bluebirds (above) to king eiders (below), males are more colorful than females—contributing to male bias among birders and scientists. Ignoring females of species like the golden-winged warbler (bottom) threatens their survival.

IN THE EARLY 1960s, at age 6, Kenn Kaufman began to spend much of his time watching birds—or, more precisely, watching male birds. “The male cardinals were bright red. The male robins were sitting out in the open and singing. For a little kid crazed about birds, and who didn’t own binoculars, I was naturally drawn to males,” he says.

Over the following decades, Kaufman, now a world-renowned birder and field guide author, observed a similar bias among his avian-obsessed colleagues of all ages. With male birds usually brighter and more conspicuous, a tendency to overlook the so-called fairer sex “is largely unconscious,” he says. “But the bias is magnified by the fact that bird guides and other reference materials—even works of art—emphasize male birds.”

That male favoritism extends to the scientific study of birds and to natural history museum collections that many researchers—in fields ranging from genomics to evolution—rely on. In a 2019 study in the Proceedings of the Royal Society B, investigators examined the bird collections of five of the world’s leading natural history museums. They found that 60 percent of those specimens were male.

According to Shannon Hackett, curator of birds at Chicago’s Field Museum (one of five museums included in the study), underrepresenting females in collections impacts the results of studies based on them. “As we’ve discovered in human medicine, the assumption that females are just subsets or small versions of males is not true, and it’s not true in studies of birds,” she says. As new technology emerges, bird specimens provide increasing amounts of data that could be affected by gender bias. “There are so many things we can learn from them now that you couldn’t dream of 100 years ago, when many were collected and we didn’t even know the structure of DNA,” says Hackett. “You can take a tiny piece of skin off the foot of a dead bird, for example, and sequence that species’ entire genome.”

One area of inquiry long affected by male bias has been the study of bird song. For more than a century, scientists considered singing to be primarily, if not exclusively, a male trait used to defend territory or attract mates. In the past two decades, however, research increasingly has revealed that in many species, both males and females sing, particularly in the tropics. Such discoveries have been spurred in part by the Female Bird Song Project, a community science effort to collect and document recordings of female birds launched in 2017 by Leiden University associate professor Katharina Riebel and University of Maryland, College Park postdoctoral researcher Karan Odom.

An image of king eider swimming.

The consequences of male favoritism may be more worrisome when it comes to conserving birds, especially neotropical migrants such as warblers, which spend summer in the United States or Canada and winter in the Caribbean, Mexico, Central or South America. According to a 2019 study published in Biological Conservation, between one-third and two-thirds of North America’s most-vulnerable neotropical and other migratory landbird species segregate sexually during the nonbreeding season, meaning males and females spend those months in different locations. Yet just 8 percent of the conservation plans for those species consider sexual segregation, focusing primarily on where the males are, says lead author Ruth Bennett, a research ecologist at the Smithsonian Migratory Bird Center.

To explore possible consequences of this oversight, Bennett and her colleagues took a close look at the plight of golden-winged warblers, diminutive and declining songbirds whose conservation plans target male habitats. Assessing more than 1,000 locations in five Central American countries during three winters, they found that females consistently took refuge in low-elevation forests that are more vulnerable to destruction. As a result, from 2000 to 2016, females lost twice as much winter habitat as males.

Those findings have implications for other neotropical migrants: “For most species where we have data, females are relegated to drier and more fragmented habitats, which are often more threatened,” Bennett says. Inspired by Bennett’s work, Joanna Wu, a Ph.D. student in ecology and evolutionary biology at UCLA, is analyzing male versus female bird survival, finding so far that females have lower survival rates across 70 species.

She and some of her colleagues who study birds say male bias could stem in part from the field’s dominance by men. “Ornithology is not a welcoming place for everyone,” says Hackett, who tries to attract more women to pursue careers like hers by mentoring young people. Groups such as the Feminist Bird Club and In Color Birding Club are promoting similar inclusivity among bird watchers. (See "NWF News: What to Read, Watch and Listen to This Spring" and "Birders in Living Color.")

To encourage all birders to better appreciate female birds, a handful of young scientists, including Wu, participate in the Galbatross Project, which organizes talks and other educational events online and in person. This Memorial Day weekend (May 25–27)—when competitive birders select a day to try and tally as many species as possible—the group will sponsor its fifth annual Female Bird Day to promote more identification of and research on what they call “the most misunderstood birds in North America.”

Longtime birder Kaufman also supports the cause, authoring an essay in Audubon, for example, confessing his own former male bird bias and sharing the benefits of paying females more heed. After all, he says, once you look beyond obvious behaviors like “acting all macho, most of the interesting things—such as producing the next generation—are being done by female birds.”

Laura Tangley is the senior editor of National Wildlife.