Two of these birds are closely related to each other. The third is a distant cousin. Don’t blame yourself if you don’t know which is which. Ornithologists just barely found out—and even the birds are confused about it.

Scientists have known about mimicry for a long time. Some species mimic the scenery to avoid being seen by predators. Others mimic a tougher member of another species so the predators that do spot it are too intimidated to try anything. Recently, a new form of mimicry has come to light. Scientists are cataloging instances of something called interspecific social dominance mimicry. These birds are the latest example.

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Three kinds of woodpeckers—the lineated woodpecker, the robust woodpecker, and the helmeted woodpecker—look very much alike. They live in the same areas. They eat the same food. Biologists naturally considered them to have developed as variations arising from a single root ancestor. But one ornithologist, Mark Robbins, upon spotting a helmeted woodpecker in a national park, was surprised when it gave out a call that was nothing like the calls of the other two woodpeckers.

When he and two other biologists took a look at the birds, they found that the helmeted woodpecker was, genetically speaking, the odd one out. It was also the smallest and weakest of the three species. The scientists believe that this bird evolved to mimic the other two not to fool predators but to fool the other birds. Even if it couldn’t put on bulk, it could change its outfit to look, if seen quickly, like a male of their own species, and not the weakest kid on the block. Meanwhile, it could use its call to distinguish itself.

[Source: Phylogenetic Relationships of the Helmeted Woodpecker.]

Image: K. Zimmer and R.J. Moller

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