Animal Equality: What Hummingbird Females Do to Avoid Sexual Harassment

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White-necked hummingbirds fan out their tail feathers when looking for a partner - and also when fighting

Photo: Brian L. Sullivan / Macaulay Library Cornell Lab of Ornithology

To outsmart pushy male conspecifics, some hummingbird females apparently use a trick: They simply wear the same plumage as the males.

That's the result of a new study published in the journal

Current Biology

.

The deception pays off

The researchers involved examined, among other things, white-necked hummingbirds, also known as Jacobin hummingbirds.

And they found out: In this species, almost 20 percent of the adult females wear plumage that looks confusingly similar to that of the males.

This strategy has two advantages: The camouflaged females would be less annoyed and at the same time would have better access to food.

How do the females do it?

"The interesting thing about white-naped hummingbirds is that all young birds have male-like plumage at the beginning," said scientist Jay Falk, a co-author of the study.

In most other bird species, the young animal plumage is more like the - usually subtle - plumage of the females.

Probably because the young animals are less noticeable to predators if they are not so brightly plumed.

When the white-naped hummingbirds are fully grown, the male birds retain their extravangant plumage.

But: Almost 20 percent of the females in the population studied in Panama do the same.

The remaining 80 percent of the females continued to develop the muted green-and-white coloration that an adult female white-naped hummingbird typically carries.

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Usually, the color of the plumage in the bird kingdom has to do with partner search and sexual selection. The scientists were able to rule out this reason in the case of female hummingbirds in men's clothing. To do this, they observed the reactions of living hummingbirds to stuffed animals that were placed on nectar dispensers during the breeding season. The preparations were stuffed adult male white-necked hummingbirds, adult females with typical female plumage, and females that looked like males.

"If the male-like plumage of the females is the result of sexual selection, then the males should have been attracted to the females with male plumage," says Falk.

“But that didn't happen.

The male Jacobin hummingbirds still showed a clear preference for the typical feathered adult females. "

Females that look like males could eat more and undisturbed

To find the reason for the plumage charade, Falk and his staff provided the birds with transmitters and set up 28 bird feeders that the transmitters could evaluate.

It turned out that the typically feathered, less colorful females were molested much more often than the females with male plumage.

With a further consequence: "Since the females with the male plumage were less exposed to aggression, they could eat more often," said Falk.

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The male-camouflaged females were able to take care of their food undisturbed and thus spent around 35 percent more time at the feeding stations.

Since hummingbirds have the highest metabolic rate among vertebrates, that can make a big difference.

The little birds have to eat constantly in order to survive.

White-naped hummingbirds aren't the only hummingbirds to experience this behavior.

According to Jay Falk, around a quarter of the more than 350 species have females that look like males.

However, the actual physical mechanism that enables females to retain male plumage is not yet known.

Just as little as the question of whether their camouflage can also be a disadvantage - if no mating partner should be found during the breeding season who does not prefer the "classic ideals of beauty".

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