Keep an eye on your thistle feeder! Those little birds feeding greedily may not be the American Goldfinches (Spinus tristis) that we thought they were. Just as in 2015, the Pine Siskins (Spinus pinus) rode the icy north winds down from Canada into Oakland Township. Some years they come; some years they don’t. Cornell Lab of Ornithology refers to them as erratic migrators who range like nomads across the continent each winter, foraging for seeds. Your finch feeder and mine are just the ticket to attract these wandering birds.
It’s easy to confuse Pine Siskins with other finches – particularly the female House Finch (Haemorhous mexicanus), which is also streaked with brown. But the smaller Pine Siskins have fine, sharp bills rather than the heavier bills of other finches, and their wings flash yellow as they scrabble with other birds at your feeder. While American Goldfinches sport some yellow feathers even in winter, they have clear breasts, not striped ones. Ben reminded me that the gregarious Pine Siskins also have a distinctive wheezy, high twitter and a distinctive “Zhreee” call that accompanies their feeding and flight. Check out the differences between these bird species below. (Click on photos to enlarge; hover cursor for captions.)
Pine Siskins have developed some pretty powerful winter survival strategies. Cornell Lab of Ornithology says that they get through frigid nights by “ramping up their metabolic rate,” which is already 40% higher than other songbirds their size. “When temperatures plunge as low as -70°C (–94°F), they can accelerate that rate up to five times normal for several hours.” Plus they’re big eaters! They gain 50% more winter fat than other finches and can stuff their crops with “seeds totaling as much as 10% of their body mass…. The energy in that amount of food could get them through 5–6 nighttime hours of subzero temperatures.”
I try not to worry too much if the Pine Siskins monopolize our feeder for a while. So far, the American Goldfinches seem to find their moments to feed. And Pine Siskins pester their own kind as readily as they do their finch relatives, as you’ll see in the slideshow below! (Click on the pause button if you need more time for captions.)
So enjoy these feisty little travelers while you can. You never know where they’ll spend next winter!