A new study zeroes in on those odd times when bird flocks bypass their usual winter habitats because of the climate.
Pine siskins are small songbirds that settle sometimes outside their normal winter hangouts.
Walt Koenig, a senior scientist in Cornell University’s ornithology lab, has long wondered why this happens with pine siskins and other bird species. He suspected it was for food, but he couldn’t decipher the patterns.
“Some years there are just incredible numbers of these birds, very large numbers, in places where they usually aren’t,” he says. “And other years, they hardly see any of them.”
Biologists teamed up with atmospheric scientists about three years ago, and they’ve now published a scientific paper that helps solve the mystery.
Court Strong, a University of Utah atmospheric scientist and lead author for the study, says the odd migrations called irruptions are tied to big climate patterns.
“It’s long been thought that these climate anomalies can affect seed crop size,” he explains. “And, when the birds arrive in the fall, they look to see what the seed crop is. And, when it’s not large enough to support their population, they’ll move.”
The study team relied on millions of observations from Project Feederwatch, a nationwide citizen science effort that keeps tabs on birds visiting backyard feeders during the winter. Strong says that invaluable data makes bird migration a new window how on the climate patterns affect our world.
“It’s like sea ice in a way. It’s a very visual example of how the natural system responds to climate change. We can see sea ice in decline, and certainly we can see birds at our feeder.”
The study found that irruptions happen two to three years after especially harsh winters.
It was published in the online Proceedings of the National Academy of Sciences.