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An adult female white-necked Jacobin hummingbird is no stranger to invisible labor.
When laying eggs, the male hummingbird, which plays an equal role in the conception of the egg in question, is nowhere to be seen. It is only thanks to its weaving hours that the egg has a nest. When the chick hatches, it will feed it alone with bait spewing from its long beak.
And then there’s the constant harassment. While quiet green females visit the flowers to sip nectar, they are chased, pecked, and body slammed by aggressive males of their own species, whose heads are a flashy blue.
But some white-necked female Jacobins found from Mexico to Brazil have a trick on their wings: Instead of wearing green feathers on themselves, they get bright blue trim and look essentially the same as male hummingbirds. According to an article published in the journal Thursday, scientists found that these male peers avoided harassment against green women. Current Biology.
For the past 50 years, most scientists have relied on the theory of sexual selection or mate selection to explain why so many male birds have snobby traits, such as a peacock’s tail feather mirage or a hummingbird’s sapphire-blue head. Jay Falk is a postdoctoral fellow at the University of Washington and author of the paper. Dr. Falk led research on the paper as a graduate student at the Cornell Laboratory of Ornithology and while working with the Smithsonian Tropical Research Institute.
But these theories can be shattered when applied to female birds that can evolve their own ornaments for evolutionary advantages unrelated to male mate-seeking.
Dr. “If we focus too much on males and sexual selection, we will inevitably miss the big picture and fail to provide a comprehensive view of nature,” Falk said. In his eyes, the antidote is social selection: a theory that sees the social life of the entire species as a driving factor in evolution.
At Indiana University in Bloomington, Dr. “The assumption that these exaggerated traits are related to sexual selection is something that needs to be tested,” said Kimberly Rosvall, a biologist who was not involved in Falk’s research. “Women compete in all kinds of contexts, but only some of them have to do with competition for mates.”
The white-necked Jacobin weighs a nickel and a penny, and the men are as tall as a roll of toilet paper. Birds are also hams, often fanning their tails and turning their backs to show off. Dr. Falk calls them “athletes of the hummingbird world.”
But their varying coloration among females is a long-standing mystery. Dr. During his studies, Falk paper It was published in 1950 describing a mix of white-necked female Jacobin hummingbirds. Some were green, but others were so convincingly male that the original collectors underlined the ♀ symbol twice for emphasis alongside a blue-headed female specimen.
In 2015, to investigate why female Jacobins resemble males, Dr. Falk traveled to the town of Gamboa, Panama, one of the more accessible haunts for hummingbirds.
Dr. After identifying the sex of 401 birds that visited feeders around town and in a nearby forest, Falk found that about 28 percent of all females resembled blue-headed males. More specifically, all juvenile females have the flamboyant blue plumage of the males, while the ornamentation is down to 20 percent of adult females. So all the fledglings looked like males, but most turned a soft green as the females grew older.
The discovery of male-like youth was not compatible with the idea of sexual selection.
Dr. “Friends wear this beautiful ornament when they don’t care at all,” Falk said.
Dr. Falk wanted to see how the Jacobins would react to the greenbirds and the flamboyant bluebirds. He painted clay mounts in the style of birds, but the birds did not act artistically or sexually. So he turned to taxed mounts, placing combinations of green females, blue males, and blue females in mangers to see how passing hummingbirds would react.
If sexual selection were involved, Dr. Falk had assumed that male hummingbirds would prefer flamboyant, masculine females. But males had a clear sexual preference for green females. Jacobins and other bird species have directed territorial aggression against green females more frequently than blue females and males, regardless of the mount’s sex, although they don’t know why.
These experiments matched the researchers’ images of white-necked Jacobin chases in the wild; this revealed that green females were chased 10 times more often than their blue-headed relatives.
Blue-headed females clearly enjoyed more personal space, but did they have any other benefits? To test this, Dr. Falk monitored the feeding behavior of green females, blue-headed females, and blue-headed males using implanted tracking tags. An analysis of 88,000 feeding visits over nine months revealed that blue-headed females made more frequent and longer visits to feeders than green females.
Forget men; The ultimate driver of female ornamentation in white-necked Jacobin hummingbirds seems to be food. Blue-headed females feed longer and chase less – a boon for a bird. burns with energy like the others.
Dr. “Hummingbirds live energetically on the edge,” Rosvall said. “A very small advantage in obtaining food is a real advantage.”
The question of how exactly some females stay true to their male coloration remains a mystery. Dr. Falk said he hopes to investigate the mechanism behind these feathers.
If you see a green Jacobin and a blue-headed Jacobin in the wild, they may look like a mating pair. But they can also be two women, and they pass their days unaffected by everyone’s assumptions.
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