Due to the abundance of snow, my feeders have been busy lately. It’s been a good winter for common redpolls. They are close cousins of American goldfinches and pine siskins, which both breed in Maine. Redpolls nest in the subarctic but wander south in winter.

These three small finches are fond of nyjer seed. Nyjer is often called thistle, because this imported seed looks much like our native thistle. It’s actually the seed of a daisy that grows in Africa and Southeast Asia. Naturally, it’s expensive, because it has more frequent flyer mileage than you do.

The mix of goldfinches, siskins and redpolls at the feeder changes each winter, and even from month to month. Lately, I’ve had a couple of siskins, a handful of goldfinches and railroad cars full of redpolls. They are highly entertaining because they descend on feeders like a plague of locusts. Many of our feeder birds sneak in warily, grab a seed and skedaddle back to cover. The finches rely on their numbers to spot trouble coming, so it’s common for them to arrive in big flocks and chow down with wild abandon.

I have long wondered if I’m getting the same flock every day, or if the finches are wanderers and I’m just getting random flocks that happen to be flash-mobbing the neighborhood. A month ago, a strange redpoll showed up with about fifty normal ones. This piebald individual was missing pigment around his face. He was eerily white in places he shouldn’t have been. He’s been coming back ever since, providing plenty of evidence that the same bunch of redpolls is wolfing down my nyjer. They’ve probably got a bunch of favorite places and feeders in the area and just make the rounds according to conditions.

This coincides with another observation. The redpolls usually arrive at the house and alight at the top of the oaks. They chatter and whoop it up for a while, probably to get the flock grouped together, then all drop at once to feed. It is such a routine that they must be quite familiar with my backyard.

When the redpolls get going on the nyjer, it would be cheaper to simply empty my wallet into the feeder. I see a lot of them. For those less experienced with the species, redpolls are about the size of a chickadee. They are brown and streaky. Both genders have red caps, though the male’s is brighter. Adult males also have a rosy tinged breast. A goldfinch in its dull winter plumage lacks streaks and stands out from the redpolls. A pine siskin, however, also is brown and streaky. They are easy enough to distinguish from redpolls through a clean window, but my window is seldom clean. According to my household schedule of chores, the next window washing is in 2017. So I squint through the grime and look at the bill. The bill of a redpoll is yellow, short and conical. The siskin bill is darker, thinner and more sharply pointed.

The real treasure hunt involves another species. When I first saw the piebald redpoll, my heart leaped at the chance that it was a hoary redpoll. I realized quickly that it wasn’t, but here is what you should be looking for. Hoary redpolls are very similar to common redpolls. Their range extends even farther north in Canada, but they overlap on the southern end of their nesting territory. They are a bit frostier in color, and that’s the thing to look for. Scan the flock and see if one looks whiter.

Examine that one closely. Plenty of individual common redpolls look whiter than their buddies, so don’t rely on that one characteristic. I find that the streaks on a hoary are much finer, sometimes barely perceptible. The bill is shorter. It looks “pushed in,” giving it a more pug-faced look than the others. Notice the butt when a bird spreads its wings while foraging or squabbling. The common redpoll’s butt is streaky brown. A hoary’s is more white and less streaked, which also is true of the underside of the tail.

Hoary redpolls are rare and they take practice to identify. I’ve only seen a few in Maine, and it’s been several years since I saw the last one. But I keep looking. After all, there is 4 feet of snow on the ground. How else am I going to pass my time this winter?

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. Bob developed the Maine Birding Trail, with information at mainebirdingtrail.com. Bob can be reached at duchesne@midmaine.com.