Female songbirds are more likely to sing when they share parenting responsibilities and live year-round in stable tropical environments, according to new research by University of the Pacific Assistant Professor of Biology Karan Odom.

The findings, published today in the journal Nature Communications, shed light on the evolutionary reasons behind female birdsong.

The research builds on earlier work Odom published in 2014, which challenged the long-held belief that birdsong evolved solely as a male trait used to attract mates and compete with rivals. The earlier study showed not only did female song emerge early in the evolution of songbirds, but in species where females no longer sing, the trait was lost over time.

Her latest study reveals that female birds are more likely to sing when they live all year in tropical climates and co-parent their young. In species that migrate and have short breeding seasons, or where females shoulder the bulk of parental duties—such as raising offspring on their own—they may sing less.

Does that mean female birds are sometimes too busy to sing?

Odom says, “Not exactly, but separate parental and territorial roles do appear to lead to differences in male and female behavior. Some birds have the same mate all year or for multiple years, which leads to males and females acting more similar. But if the birds are not monogamous, if the male breeds with multiple females, then we have observed that their traits diverge, and we find support that the male gets a really flashy, complex, long song, and the female gets a short song, or she loses her song,” Odom said.

“They might just breed once and then go and find another mate, and then the female, in those cases, does all the work on her own: she's raising the chicks and feeding the chicks, and that would be where you observe less female song. This might be because when the female spends so much time around the nest, it is detrimental to sing.”

The study also identifies male parental care as a key factor driving the evolution of female song, suggesting that females might use song to attract not just any mate, but one likely to help raise young.

“I get excited about the parental care being significant because that's not something people have tested before. That’s a new result, and it reaffirms that females could be competing for good mates or good dads,” Odom said.

Traditionally, female birdsong is an understudied area in the field, an issue Odom discussed with National Geographic earlier this year.

“I truly love my work,” Odom said. “I feel very passionate about it. It's a field I've been in for about a decade now, and I self-selected it out of pure enthusiasm. I went where the questions guided me and what I found most exciting, and then I spend a lot of time and energy on the research. It feels good to have that work recognized and get to the point where I've made a big enough contribution that it could get into a journal like Nature Communications.”

Odom, who comes from a liberal arts background, said she values weaving her research into her teaching at Pacific.

“Before I went to undergrad, I didn’t know a career in science was possible,” she said. “Being at a smaller university where I got to interact one-on-one with faculty helped me realize it was not only possible but attainable. I got to participate directly in research and receive hands-on training from scientists. It was an environment I really appreciated.”

Odom said she works to create the same opportunities for her students.

“I’m really enjoying my time at Pacific. I also enjoy being on the other side—working with students one-on-one,” she said. “This research is attractive, graspable and a great introduction to more complex scientific theories. It helps students get excited about science.”