Female hummingbirds ‘disguise' themselves

Considering their daintiness, it might surprise you to learn that during mating season male hummingbirds can be pretty violent bachelors, pecking and body slamming the apples of their tiny eyes (they can shimmy through waterfalls though so pretty tough, I guess). To avoid the excessive advances, it seems the females have found a clever way of flying under the males’ radars by upgrading their plumage to match the brightly colored courting clothes of males on the prowl. Clever girls…

The discovery comes as part of a new paper published in the journal Current Biology. The team on the research were focusing on white-necked Jacobin hummingbirds in Panama, a species that usually exhibits sexual dimorphism meaning the males and females look different from one another.

The females are usually a more muted colorway of greens, grays, and blacks compared to the flashy iridescent blue of the males, which is offset against vibrant white on the tail and belly. That is, it seems, unless the females have had quite enough of being pushed around by amorous males.

“One of the ‘aha moments’ of this study was when I realized that all of the juvenile females had showy colors,” said first author Jay Falk, who led the research as a part of the Cornell Lab of Ornithology and Smithsonian Tropical Research Institute, in a statement.

“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.”

Their investigations revealed that around 20 percent of adult females had opted for the male plumage, failing to switch from the showy colors of their youth to the muted feathers of female adulthood as is the norm for 80 percent of females. Whether the switch, or lack thereof, is due to genetics, the environment, or an active choice on the part of the female isn’t clear yet, but the researchers hypothesize it’s likely related to females wanting to avoid harassment while feeding or during mating season.

To reach their conclusions, the team set up decoy hummingbirds to see how real hummingbirds reacted to them. The method revealed that the fake hummingbirds with the female-type plumage were far more likely to be harassed than their flashy counterparts.

That females have flashy feathers when they are young and not looking to mate demonstrates that the male plumage doesn’t glean a sexual advantage, so the birds must be exhibiting these feathers for a different reason. Social selection is one possible explanation, painting a picture that the male feathers gain the birds a social benefit in that they don’t get beaten up at mealtimes by bolshie boy birds.

“Hummingbirds are such beloved animals by many people, but there are still mysteries that we haven’t noticed or studied,” says Falk. “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.”