Some female hummingbirds trick males to avoid harassment, study finds. Here’s how - Mahoning Matters

The way birds’ feathers glitter in the light, their unique array of colors and the patterns they display are usually sexual in nature, intended to capture the attention of the perfect mate.

But some birds use their plumage for more urgent priorities — like blending in with the opposite sex to dodge physical harassment from aroused and hungry males, a feat unique to female white-necked Jacobin hummingbirds, according to a new study published Thursday in the journal Current Biology.

Regardless of sex, most bird species are born with dull-colored feathers typical of adult females, likely in an effort to evade predators, experts say. But all white-necked Jacobin chicks emerge from their eggs with iridescent blue heads typical of adult males.

As the hummingbirds mature, all males keep their vivid colors — as do some females. In the new study, 20% of them kept the flamboyant plumage of their youth.

“For birds that’s really unusual because you usually find that when the males and females are different the juveniles usually look like the adult females, not the adult males, and that’s true almost across the board for birds,” study lead author Jay Falk, who conducted the research as a Ph.D. student with the Cornell Lab of Ornithology, said in a statement. “It was unusual to find one where the juveniles looked like the males. So it was clear something was at play.”

The team studied more than 400 white-necked Jacobin hummingbirds in Panama between July 2015 and June 2019. Data was collected via observed reactions of live birds interacting with fake stuffed ones perched on nectar feeders during breeding season. Researchers also placed radio frequency tags on some birds and designed a circuit of 28 feeders wired to the tags to track the number and length of visits.

Several days of observation and experimentation later, researchers discovered females that sported male-like feathers got to feed on nectar posts for about 35% longer than typical adult females.

“Because the male-plumaged females experienced less aggression, they were able to feed more often — a clear advantage,” Falk, who is now a postdoctoral fellow at the University of Washington, said in a statement. Males often harass females by pecking them with their beaks or body slamming them.

The difference in feeding time can mean life or death, researchers say, because hummingbirds have to eat constantly to survive; their metabolic rate is higher than any other vertebrate, including mammals, birds, reptiles, amphibians and fishes.

Typical-looking females were also chased away from feeding posts by males 10 times more often than those that had male-like feathers.

It’s unclear if the disguise is genetic, due to environmental factors or an intentional choice females can control. It’s also unclear if the trickster females mirror the aggressive behaviors typical of males, but researchers suggest the act is social in nature — “they avoid the bullies by looking like them.”

“If females having male-like plumage is the result of sexual selection, then the males would have been drawn to the male-plumaged females,” Falk said. “That didn’t happen. The male white-necked Jacobins still showed a clear preference for the typically plumed adult females.”

White-necked Jacobins aren’t the only masters of disguise, Falk said. About 25% of the world’s more than 350 hummingbird species also have some females that take on male appearances.

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