It’s possible to conduct science just by staring out your kitchen window, coffee cup in hand. Project FeederWatch is a citizen science survey where average citizens simply look at the bird feeder and occasionally count what they’re seeing. The survey happens in winter, when large flocks of birds are meandering all over the continent.
The premise is simple. The birds have to be somewhere. If they’re not at your house, they’re at somebody else’s, perhaps several states away. The Cornell Lab or Ornithology started Project FeederWatch as an easy way to track movements and trends. Based on thousands of reports from households all over the country, they can get a sense of where these winter wanderers are going. They can also detect if populations are growing or declining. Over 20,000 households now participate nationwide.
For instance, there are roughly 40 American goldfinches outside my window right now, gobbling down Nyjer seed from my thistle feeders, and seriously denting my wallet. But I’ve had only two pine siskins all winter, and no common redpolls. For wandering finches, every winter is different. In some years, I get loads of siskins. In other years, I can have flocks of up to a hundred redpolls. Wherever those birds are this winter, they’re not at my house.
One benefit of joining the project is that you get email explanations of what’s happening in the bird world. One that crossed my desk last week asked the question, “Why do downy and hairy woodpeckers look so similar when they aren’t close relatives?” Umm, I dunno. Why?
It never occurred to me that they are not closely related. Although the downy is much smaller, they share a similar black-and-white pattern and a red patch on the back of the head. The downy bill is conspicuously shorter, but otherwise, they look like the recent descendants of a common ancestor.
Genetic analysis reveals that each is much more closely related to other woodpecker species than they are to each other. If genes inherited from a common ancestor aren’t the answer, then how did they come to resemble each other so closely?
Researchers at Project FeederWatch guessed that there must be some advantage for a downy to look like a hairy. Since they often visit the same feeders, and forage in the same trees, perhaps the downy evolved to look like a hairy so the bigger birds wouldn’t bully them. Perhaps the hairy would be fooled by the resemblance, think the downy is an equally tough hairy, and leave it alone.
So they put their volunteers to work. FeederWatchers were asked to watch what happened when both species showed up at a feeder at the same time. If the hypothesis was correct, then observers would see them coexist peacefully.
They didn’t. Hairy woodpeckers chased off downy woodpeckers about as often as they chased off everything else. So the researchers guessed again. Downy woodpeckers are aggressive for their size, able to displace larger birds at the feeder. Maybe a downy wasn’t fooling the hairy, but he was fooling other birds.
So FeederWatchers watched again. This time, anecdotal observations did show that downy woodpeckers drove off larger birds. Woodpeckers have long pointed bills meant for striking. In a skirmish, that’s a handy weapon, so it’s not completely surprising that a downy would win a face-to-face confrontation with a much larger cardinal. But many observers noticed that larger birds would vacate the feeder as the downy was flying in. This reinforced the notion that perhaps some birds thought the larger hairy was approaching and they decided to skedaddle before a fight. There’s not enough evidence to draw a conclusion; more research is needed.
The world shows many examples of convergent evolution, when two unrelated species evolve to look like each other. It may be caused when two species evolve with similar habitat requirements, and therefore develop similar features. Dowitchers, snipes, and woodcocks all have absurdly long bills, but only because they probe in mud. Vultures in Eurasia look very much like vultures in North America, yet they share no kinship. Old World vultures are in the hawk and eagle family. New World vultures are closely related to storks.
In some cases, one species actually benefits by looking like another. Monarch butterflies are poisonous to the predators that would eat them. Viceroys aren’t poisonous, but they’ve evolved to look like monarchs, and predators leave them alone, not recognizing the difference.
If you’d like to conduct a little science out your own window, visit www.feederwatch.org.
Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at firstname.lastname@example.org.
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