Text message from my friend Miranda: Would a snow goose perch on top of a telephone pole?
Me: Gee, I don’t know. I’ll find out.
I pose the question to my bird-watching friend Rob, who’s spent more time looking at the world through glass lenses than Galileo. Miranda thinks she saw a snow goose on top of a telephone pole. Do they do that?
Rob: Is she sure it wasn’t a snowy owl? This is an irruption year, remember.
Ah, yes. The irruption, when birds end up in places where they’re not normally found, sending hardcore birders into a tailspin. Rob was in the middle of hunting down another unusual migrant when I reached him, tracking a gyrfalcon in Berks County, so he made me promise to get GPS coordinates for the pole in question from Miranda.
By definition, irruptions are irregular and dramatic. So when snowies come down from the Arctic, they do it in migration patterns that can’t really be predicted, sometimes in great numbers. The largest irruption on record occurred during the winter of 1926-27, when 39 of the birds were spotted in Pennsylvania.
In 1945, an ornithologist named Shelford came up with an elegant way to explanation this oddly nomadic owl behavior. He said snowies move south because of population crashes in their favored prey: lemmings.
What’s a lemming? Kinda like an Arctic hamster. Here’s a picture from Wikipedia.
This makes perfect sense to me. After all, ever since the nearest Papa John’s closed its doors, I’ve experienced my own personal irruptions into Wilkes-Barre—the next closest location for this franchise—whenever I get hungry for some good pizza. Can’t get food here. Go where food is.
But scientists now believe this explanation is oversimplified. This year’s irruption for example comes on the heels of a lemming population high. Lotsa lemmings leads to greater nesting success for snowies. More adorable little owlets survive to eventually compete with their parents for adorable Arctic hamsterfood. Some young birds get the boot and head south. This explains why immature snowy owls tend to make up the bulk of birds found in each irruption year.
To further our analogy, let’s say Papa John’s is having a banner year. They open franchises all over the place, and eventually everybody and their brother is hooked on pizza and cheesy bread. The joint gets crowded, so a bunch of old-timers (me included) tell the kids to go find their own hang out. Now the young folks are the ones who end up all the way out in Wilkes-Barre. They’ve irrupted.
Age does have its privileges.
Snowy owls do eat things other than lemmings, just as I could go to Domino's or Pizza Hut, and this tends to complicate things further. But the cyclic nature of lemming populations does play a role—not that it helps clear things up, considering the reasons behind this cycle are equally mysterious.
Just ask Charlie Krebs. He’s an ecologist who’s spent the past 45 years (45 years!) trying to figure out what makes lemming populations tick. Yes, in a world full of great-white sharks, African lions and Tyrannosaur fossils, this guy has spent a lifetime chasing pudgy little rodents across the frozen tundra. Good for him, I say.
Oh, wait! Krebs does admit to taking a 20-year break from his research to study arctic hares. Then again, he was only tracking the hares so he could better understand (wait for it...) lemmings.
In an interview for Uphere magazine, Krebs sums up decades of research into Arctic ecology thusly:
“We like to think the world is really simple—that human beings are complicated and everything else is simple. But that's just wrong. To sort out what seem to be these straightforward problems takes a very long time.”
Longer than 45 years I suppose because Krebs is still at it. Imagine spending all that time so far north; the cold, the wind, the isolation, and I bet not a snowball’s chance you could convince Papa John’s to deliver up there.