Cornell Lab of Ornithology scientists found evidence that some woodpeckers evolve to look like another species of woodpecker in the same neighborhood.
The researchers say that this “plumage mimicry” isn’t a fluke – it happens among pairs of distantly related woodpeckers all over the world.
“Habitat, climate, and genetics play a huge role in the way feather color, and pattern develop,” explains lead author Eliot Miller at the Cornell Lab.
“Species in similar environments can look similar to one another. But in some cases, there’s another factor influencing the remarkable resemblance between two woodpecker species, and that’s mimicry.”
He says it’s the same phenomenon found in some butterflies which have evolved markings that make them look like a different bad-tasting or toxic species to ward off predators.
230 Woodpecker Species Studied
Study authors combined data on feather color, DNA sequences, eBird reports, and NASA satellite measures of vegetation for all 230 of the world’s woodpecker species.
It became clear, Miller says, that there have been repeated cases of distantly related woodpeckers coming to closely resemble each other when they live in the same region of the globe.
“In North America, the classic lookalike pairing is Downy Woodpecker and the larger Hairy Woodpecker,” Miller says.
“Our study suggests that these two species have evolved to look nearly identical above and beyond what would be expected based on their environment. Yet, these two species evolved millions of years apart.”
Other North American lookalikes are Black-backed and Three-toed Woodpeckers.
In Europe, Greater and Lesser Spotted Woodpeckers bear a striking resemblance, as do the Lineated, Robust, and Helmeted Woodpeckers of South America.
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Explanation for Woodpecker Doppelgangers
Miller’s explanation for woodpecker doppelgangers is that Downy Woodpeckers that look like the larger, more aggressive Hairy Woodpeckers might make other birds, such as nuthatches and titmice, think twice about competing with the downy for food.
Some evidence supporting this idea has been found in observational studies, but field experiments would be needed to more conclusively test this hypothesis.
The data turned up some other interesting connections between woodpecker appearance and habitat.
Many of the woodpeckers the scientists looked at in tropical regions have darker feathers.
This adds to a growing body of evidence in support of “Gloger’s Rule,” stating that organisms tend to be darker colored in more humid areas.
Other Woodpecker Findings
They also found that:
- Red-headed woodpecker species tend to live in forested habitats
- Black, white, and gray colored species tend to live in open habitats
- Woodpeckers with red on their bellies are most often found in forests
- Woodpeckers with large patches of color on their bellies were most often found in open habitats
Additional studies are needed to try to determine why some plumage patterns seem to be linked to habitat types.
Miller says it’s really fascinating and pretty likely this is happening in other bird families, too.
“I first got interested in this question a decade ago from looking through bird books. I wondered how the heck some distantly related species could look so much alike – what are the odds that it could happen just by chance?”
Read the study published in Nature Communications.