Female hummingbirds imitate males — to avoid harassment from doting mate-seekers

by John Anderer (studyfinds.org)

ITHACA, N.Y. — The “catcall” is as outdated as it is cringeworthy. Interestingly, however, a new study finds human females aren’t the only ones who have to deal with unwanted advances. Researchers report that many female hummingbirds display the same bright colors as males — all to help avoid unwanted behaviors from males looking for a mate.

This research focused on white-necked Jacobin hummingbirds living in Panama. Over a quarter of studied females had coloring usually associated with male hummingbirds. Researchers say these colors keep doting males from harassing females with common behavior such as pecking or body slamming.

“One of the ‘aha moments’ of this study was when I realized that all of the juvenile females had showy colors,” says first study author Jay Falk, currently a postdoc at the University of Washington, in a media release. Mr. Falk led this research when he was a part of the Cornell Lab of Ornithology and Smithsonian Tropical Research Institute. “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. It was unusual to find one where the juveniles looked like the males. So it was clear something was at play.”

Male hummingbirds leave flashy-colored females alone

Male white-necked Jacobin hummingbirds are known for their bright, distinctly flashy color patterns, usually characterized by beautiful blue head markings, and a bright white tail and stomach. Adult females, meanwhile, aren’t as colorful, usually displaying more muted tones of gray, green, and black that work much more efficiently as camouflage.

As children, even females display vibrant colors before seeing their markings grow more muted with time. However, among the juvenile females studied by researchers, around 20 percent retained their bright colors well into adulthood. As of today, study authors can’t say exactly how or why this occurs in some female hummingbirds. It may be genetic, environmental, or entirely up to choice. That being said, researchers do conclude that whatever the mechanism, the purpose is to help avoid aggressive male behavior and harassment during feeding and mating.

“Hummingbirds are such beloved animals by many people, but there are still mysteries that we haven’t noticed or studied,” Falk explains. “It’s cool that you don’t have to go to an obscure unknown bird to find interesting and revealing results. You can just look at a bird that everyone loves to watch in the first place.”

In an experiment, the research team placed stuffed hummingbirds nearby and watched as real hummingbirds interacted with the fakes. Sure enough, males primarily harassed the fake birds with muted color patterns, and left the others alone. Additionally, most females only have bright colors as children, which is of course not a time when mating is even possible.

In the future, study authors would like to use this work to help research how differences between males and females develop across other species.

The study is published in Current Biology.