Female hummingbirds avoid harassment by looking like males

An adult female Jacobean white-necked hummingbird is no stranger to invisible work. When she lays an egg, the male hummingbird that pla...


An adult female Jacobean white-necked hummingbird is no stranger to invisible work.

When she lays an egg, the male hummingbird that played an equal role in the conception of that egg is nowhere to be found. It is only thanks to its hours of weaving that the egg has a nest. When her chick hatches, she alone will give her the food regurgitated from her long beak.

And then there’s the constant harassment. While the pale green females visit the flowers to sip nectar, they are chased, pecked, and punched by aggressive males of their kind, whose heads are a flaming blue.

But some white-necked Jacobin females, found from Mexico to Brazil, have a trick: instead of dressing in green plumage, they adopt bright blue ornamentation and appear essentially identical to male hummingbirds. Scientists have discovered that these male look-alikes avoid harassment directed at green women, according to an article published in the newspaper on Thursday. Current biology.

For the past 50 years, most scientists have relied on the theory of sexual selection, or mate choice, to explain why so many male birds have such fanciful traits, like the candling of the tail feathers. of a peacock or the sapphire blue head of a hummingbird, said Jay Falk, a postdoctoral researcher at the University of Washington and author of the article. Dr Falk led the research on the article as a graduate student at the Cornell Lab of Ornithology and working with the Smithsonian Tropical Research Institute.

But these theories can fall apart when applied to female birds, which can develop their own ornamentation for evolutionary benefits that have nothing to do with finding male mates.

“If we focus too much on men and sexual selection, we inevitably miss the big picture and fail to provide a full view of nature,” said Dr Falk. In his eyes, the antidote is social selection: a theory that views the social life of the entire species as a driving factor in evolution.

“The hypothesis that these extravagant traits have to do with sexual selection is something that needs testing,” said Kimberly Rosvall, a biologist at Indiana University, Bloomington, who was not involved in the research. Dr Falk. “Women compete in all kinds of settings, but only some of them have anything to do with competing for mates.”

The White-necked Jacobin weighs as much as a penny and a penny, and males grow as long as a roll of toilet paper. Birds are hams too, often fanning out and turning around to show off. Dr Falk calls them “the sportsmen of the hummingbird world”.

But their varying colors in females are a long-standing mystery. During his studies, Dr Falk encountered a paper published in 1950 describing a mix of female Jacobean white-necked hummingbirds. Some were green, but others were so masculine that the original collectors had twice underlined the ♀ symbol for emphasis next to a blue-headed female specimen.

In 2015, to investigate why Jacobin women looked like men, Dr Falk visited the town of Gamboa, Panama, one of the most accessible haunts of hummingbirds.

After sexing 401 birds that visited feeders placed around town and in a nearby forest, Dr Falk found that about 28 percent of all females looked like blue-headed males. Specifically, all of the young females had the bright blue plumage of the males, while the ornamentation narrowed to 20 percent of the adult females. So, all the juvenile birds looked like males, but as the females got older, most changed to a muted green.

The discovery of juveniles resembling males did not correspond to the idea of ​​sexual selection.

“They wear this beautiful ornamentation when they don’t care about their mates at all,” Dr Falk said.

Dr Falk wanted to see how the Jacobins would react to green birds and flashy blue birds. He painted clay mounts in the style of birds, but the birds were not moved – artistically or sexually. So he turned to taxidermy mounts, placing combinations of green females, blue males, and blue females on feeders to see how passing hummingbirds would react.

If sexual selection was at stake, Dr Falk speculated that male hummingbirds would prefer showy, male-like females. But the males had a distinct sexual preference for the green females. And the Jacobins and other bird species more often directed territorial aggression toward green females than blue females and males, regardless of the sex of the mount, although they don’t know why.

These experiments matched researchers’ images of white-necked Jacobin pursuits in the wild, which found that green females were hunted more than 10 times more often than their blue-headed parents.

Blue-headed women clearly enjoyed more personal space, but were there other benefits? To test this, Dr Falk monitored the feeding behaviors of green females, blue-headed females, and blue-headed males using implanted tracking tags. An analysis of 88,000 feeding visits over nine months found that blue-headed females visited feeders more frequently and for longer periods of time than green females.

Forget the males; food appears to be the ultimate driver of female ornamentation in Jacobean white-necked hummingbirds. Blue-headed females feed longer and are hunted less – a boon for a bird that burns with energy not like the others.

“Hummingbirds live energetically on the fringes,” said Dr Rosvall. “A still small advantage in the acquisition of food is a real advantage.”

The question of how, exactly, some females stick to their male coloring remains a mystery. Dr Falk said he hoped to study the mechanism behind this plumage.

If you see a Green Jacobin and a Blue-headed Jacobin in the wild, they may appear to be a mating pair. But it could also be two women, spending their days without worrying about everyone’s assumptions.

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Newsrust - US Top News: Female hummingbirds avoid harassment by looking like males
Female hummingbirds avoid harassment by looking like males
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