In a paper published on August 26, 2021, in Contemporary Biology, researchers revealed that in white-necked hummingbirds, some female birds develop plumage resembling males, with shiny blue heads and necks, possibly to avoid harassment from other birds.

Over four years, researchers from Cornell University and Columbia University captured 436 white-necked hummingbirds in Panama.

These birds, known for their exceptional flying abilities, posed a considerable challenge to catch. After measuring, tagging, and collecting blood samples, the birds were released back into the wild. Surprisingly, over a quarter of the female hummingbirds exhibited bright ornamental plumage similar to males.

Further examination showed this phenomenon of female mimicry in the hummingbird world is not uncommon. Researchers surveyed over 10,000 specimens from 307 different hummingbird species in five US natural history museums, finding a quarter of the hummingbirds displayed female mimicry. Considering nearly half of all hummingbirds show no visual differences between genders, female mimicry accounts for 40% of all visually distinct hummingbirds.

Female mimicry is not only prevalent but also not an isolated incident in the hummingbird world. This skill evolved independently multiple times across different evolutionary branches, indicating its significant benefits for female hummingbirds' survival, prompting many species to adopt it.

But what benefits does female mimicry provide? Young white-necked hummingbirds have blue-white plumage. When mature, males retain this flashy pattern, while females develop a softer green and white—though not all females. Why would some females retain the bright blue feathers and hide among the males?

To answer this, researchers placed specimens of normal and male-mimicking female hummingbirds in the wild and observed how wild males responded. The mimicry was quite successful, with wild males showing interest mainly in female-colored specimens, displaying either aggression or courtship behavior.

When male hummingbird and male-mimicking female specimens were presented together, wild males couldn't distinguish between them, displaying significantly reduced aggression towards both. Additionally, male-mimicking females experienced fewer attacks from female hummingbirds and other species, suggesting bright colors reduce aggression from males and other birds significantly.

Researchers then tagged different white-necked hummingbirds and installed 28 feeders with recognition chips in their forest habitat, recording the feeding behavior for 278 days. Statistical analysis of these records revealed that male-mimicking hummingbirds had significantly more time to feed after experiencing reduced harassment compared to other birds.

We know feeding is crucial for hummingbirds! They have the fastest metabolism among animals, 77 times faster than humans. With extreme activity levels, beating their wings 80 times per second and a heart rate of up to 1200 beats per minute, they consume twice their weight in nectar daily, requiring visits to thousands of flowers. This might explain why female mimicry is prevalent among hummingbirds while yet to be discovered in other bird species.