Maybe you’ve seen them, too: flocks of brownish birds recklessly swarming on the sandy shoulders and even the traveled lanes of snowy roads. They don’t move until the last possible second, and sometimes that’s too late.
At the Museum, we’ve been debating their identity. I’ve seen flocks of snow buntings lately, but those are black and white. Last week, Jayme Morey, Collections Assistant at the Museum, decided that the solution to our curiosity was to bring in one of the slowpokes off the side of the road to get a better look. With the help of Diane Kraemer, our other Collections Assistant, she identified the tiny, five-inch long corpse as a pine siskin, Spinus pinus.
Despite their lack of even a four-year-old’s understanding of traffic safety, pine siskins have some amazing strategies for winter survival. And because they normally live in the remote forests of Canada, you can’t blame them for being naïve about cars. These little finches do have powerful engines, though. They can survive negative 94 degree Fahrenheit nights by revving up their metabolic rate to five times normal for several hours. That’s 40% higher than other “normal” songbirds.
In order to fuel those internal fires, pine siskins put on 50% more winter fat than their cousins—common redpolls and American goldfinches. They also store a bedtime snack right in their esophagus—in the expandable section called the “crop.” But it isn’t just a single cookie and glass of milk; their crop can store seeds equal to 10% of their body mass. Those calories could get them through five or six hours of sub-zero temperatures.
Having enough fuel to fill their crops and fuel their engines is the key to survival for pine siskins. That is what brought them south, to Northern Wisconsin. In the face of winter and diminished food supplies, every animal must choose between three basic survival strategies: hibernate, migrate, or stay active. Pine siskins have adapted to migrate, but not in the regular, biannual travels between particular places like common loons. Pine siskins “irrupt” in irregular migrations every couple years to wherever the food supply is greatest.
When their typical winter food supplies in Canada are low, pine siskins may flock into New England, the upper Midwest, or even the southeastern United States. They are looking for plentiful supplies of seeds from pines, cedars, larch, hemlock, spruce, alder, birch, and maple. This year, I’ve seen lots of hemlock cone scales littering the snow. This tells me that there’s a good crop of hemlock cones, and that many critters are taking advantage of the bounty.
Just as the boom and bust cycles of acorns kept passenger pigeons on the move and allowed some oaks to sprout, the cycles of conifer seed scarcity in Canada may disperse siskins and reduce the birds’ long-term impact on the plants.
Pine siskins’ irruptive behavior also brings a diversion from our regular winter birds. With a touch of yellow on their wings, pine siskins look a bit like goldfinches, but they are heavily streaked on their head and body, while goldfinches have smoother colors. At your feeders, pine siskins prefer smaller seeds without tough shells, like thistle and oil sunflower.
Be sure to watch for sick birds at your feeders. The high concentrations of birds in an irruption year can help spread Salmonella bacteria. Sick birds will look thin, fluffed up, and often have swollen eyelids. If you see this, clean your feeders thoroughly (with care to protect yourself) and take them down for a week to allow large flocks with sick birds to disperse.
In the woods, listen for siskins’ wheezy contact calls, and look for their undulating flight. Flocks will often feed gregariously, and then swoop off one-by-one to the next tree. It can be hard to get a good look while they are flitting about in the tippy top of trees, in the high branches where cones are most plentiful. Still, you can admire their acrobatics as they cling upside down to bouncing branch tips.
On the road, watch out! Pine siskins are fond of minerals like road salt. So, the next time you tap your brakes for a flock of brownish birds recklessly swarming on the traveled lanes of an snowy road, at least you’ll know what you’re dodging, and perhaps give a little more credit (and space) to your fellow winter travelers.
For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! The current exhibit, “Nature’s Superheroes—Adventures with Adaptations,” opens in May 2014 and will remain open until March 2015.
Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com.