7 December 2020
Two common birds in Pennsylvania, downy and hairy woodpeckers, are so similar that they’re hard to tell apart. Downy woodpeckers are small and hairys are large but if they’re not side by side there’s just one major clue:
- Downy woodpeckers have short beaks, one third the length of their heads back-to-front.
- Hairy woodpeckers have long beaks, same length as their heads back-to-front.
Frank Izaguirre (@BirdIzLife) tweeted this recent backyard photo of both birds:
I think this is the first time I’ve ever gotten the true side-by-side with both birds within a foot of each other. The downy’s bill looks weird because it has a sunflower seed in it. pic.twitter.com/ilexbvIOiD— Frank Izaguirre (@BirdIzLife) December 5, 2020
Because of their similarity you’d think downys and hairys are close cousins but they’re not. A study published in April 2019 explains why they look alike, described in Living Bird:
Despite being look-alikes these two species are not that closely related. Their genetic lineages split off from a shared ancestor over 6 million years ago—about as far back as chimps and humans split.
A new study published in April in the journal Nature Communications provides strong evidence that Downy and Hairy Woodpeckers are an example of “plumage mimicry”—one species of bird evolving to match the plumage patterns and colors of another.— Living Bird: Are woodpeckers evolving to look like each other; a new study says yes
They don’t look like their near relatives. They look like each other.
So don’t feel bad if you can’t tell downy woodpeckers and hairy woodpeckers apart. They are mimics. 😉
See how many other woodpeckers are mimics at Living Bird: Are woodpeckers evolving to look like each other; a new study says yes.
(photos from Wikimedia Commons; click on the captions to see the originals)