In the Jacobin hummingbird, a common species in Central and South America, the male's colorful plumage normally distinguishes it from that of the rather drab female.

However, 20% of these female hummingbirds grow up mimicking the adornment of males.

A disguise that deters their male counterparts - quick to oust a competitor to access flower nectar - from attacking them, according to the study published in the Royal Society's biological research journal, "Proceedings B".

"Androchromic females (with male adornment) mimic more aggressive males to access nectar," study first author Jay Falk, from the biology department at the University of Washington.

Mimicry between species is well documented, with some adopting the characteristic appearance of another to deceive a predator, for example.

Harmless butterfly species have thus adopted colorful wing patterns similar to those of bird-poisonous butterfly species, to deter them from preying on them.

This time, which is more rarely documented with females, the case of mimicry is exercised within the same species and with social domination as the driving force.

The team of ornithologists led by Jay Falk sought to find out if the female androchrome hummingbird pushed the deception to a physical (beyond plumage) and behavioral resemblance.

Answer: nothing.

End of scheme

In some species, the change in appearance between males is correlated with physiological changes, indicative of distinct abilities or behavior.

Species of sparrows thus display plumage colors correlated with greater or lesser aggressiveness, notes the study.

The scientists compared the physical characteristics of male Jacobin hummingbirds to those of androchromic and heterochromic females, thus either looking similar or distinct from males.

They went so far as to submit them to muscular explosiveness tests... By measuring the ability of the tiny bird, renowned for its speed and aerial acrobatics, to take flight once weighted down.

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On paper, nothing distinguishes the two types of females, nor in their mode of feeding, much less territorial than that of the males.

Thus androchromic (adorning male) females "reap the benefit of appearing as an aggressive male via mimicry, without the potential cost of having to behave like him," according to the study.

In other words, the female does not have to make an effort, muscular and nervous, to ape the male, she just has to disguise herself.

This ploy normally works on the condition that a limited number of females use it.

Because otherwise, the males could realize the deception and nature try to find a parade there.

“We assume that some sort of equilibrium point has been reached in fitness (which measures its success in reproducing) between androchromes and heterochromes,” says Jay Falk.

Without excluding that the species evolves towards a perfect resemblance between the sexes, he adds.

The study notes in this regard that many species of hummingbirds have unique plumage.

© 2022 AFP