![]() ![]() Mimicry is widespread in nature, perhaps the most familiar example being Monarch and Viceroy butterflies. For some reason, two different-looking species have come to appear quite the same. This means that the more likely explanation for being look-alikes is that the resemblance is evolved. Chances are that the common ancestor of both looked quite different from either. Each is more closely related to a very different looking group of woodpeckers (cases in point: Hairy Woodpeckers are more closely related to White-headed Woodpeckers and Smoky-brown Woodpeckers than to Downy Woodpeckers), which rules out the possibility that they inherited their matching plumages from a common ancestor. In the case of Downy and Hairy woodpeckers, however, the similarities are not homologous. In other words, we assumed that these woodpeckers looked alike because they were alike. Humans have forelimbs that are anatomically similar to salamanders, cats, whales, and every other vertebrate because we share a common ancestor, not because each group independently evolved the same set of bones. Plumage similarities of the sort exhibited by Downy and Hairy woodpeckers tend to reflect a recent, shared evolutionary history in the parlance of evolutionary biologists these shared characteristics are homologous, or features inherited from a common ancestor. ![]() That these two species were not especially close relatives came as some surprise to ornithologists. Nonetheless, the point remains: they aren’t the closest of relatives ). ![]() Indeed, to find the closest common ancestor of Hairy and Downy woodpeckers, one must travel all the way back in time to the primordial Picoides woodpecker, the mother of all subsequent species in this genus (I should point out that woodpeckers are no exception to the rule that no taxonomy is ever certain one recent study argues that Hairy and Downy woodpeckers are neither in the same genus nor belong in Picoides. Hairy Woodpeckers, by contrast, are a sister to the Arizona Woodpecker and the Mexican endemic Strickland’s Woodpecker. Downy Woodpeckers are probably more closely related to two species of western North America, Nuttall’s Woodpecker and Ladder-backed Woodpecker. Hairy Woodpeckers are about 50% again as big as Downy Woodpeckers, and carry a relatively longer bill.ĭespite their close resemblance of one another, various studies have revealed that these two species are in fact not close relatives of one another. Similar in almost every feature of their plumage, they are most readily distinguishable by their size. The last two species pose a real challenge for many birdwatchers. Chickadees, Tufted Titmice, American Goldfinches, hordes of Blue Jays, a hardy trio of Northern Cardinals, and a rotating cast of Downy Woodpeckers and Hairy Woodpeckers. Then there are the regulars, always present as soon as I fill the feeders in early winter. Dozens of them have been daily at my feeders since before the snow fell, and with the storm of last week they’ve taken to perching on the feeders, a behavior I don’t recall seeing so commonly before. The feeders, though, are comparatively busy: in some winters, I’m visited by hundreds of Common Redpolls, although this year so far has been the year of the Dark-eyed Junco. Just as easily, though, I can spend an hour wandering through the snow in absolute silence the trees seem empty of birdlife. If I’m lucky, I might come across a noisy flock of Golden-crowned Kinglets, Black-capped Chickadees, and Brown Creepers. A walk through my woods in winter, although lovely in its own right, tends to yield fairly few birds. As winter descends and the days become cold and short, most of my birdwatching becomes rather narrowly focused on the feeders outside my front door. Downy Woodpecker by Wolfgang Wander, via Wikimedia Commons. Hairy Woodpecker by User:Mdf (Own work), via Wikimedia Commons. ![]()
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