GRAND FORKS — This week’s bird of the week looks quite a lot like last week’s bird of the week, and the house finch and the common redpoll do have some things in common.
They are both finches.
To say a bird is a finch is about the same as saying a person’s name is Johnson. It betrays where the person came from, but it doesn’t say much else, other than menu choices.
Like all finches, these two species are seed eaters.
Beyond these general similarities, these birds don’t have much in common, and discernment will tell them apart under most conditions.
As to appearance, both have red caps, and males of both species have a red blush on their chests. This intensifies as winter wanes, as a response to the light — and as a signal to female birds interested in securing mates.
Yet there are noticeable differences between these two species.
First, the general impression of size and shape, g.i.s.s,, as birders often say.
House finches are rather clunky birds, somewhat heavily built and with large bills adapted to seed cracking. Redpolls appear to be more — not delicate, exactly, but more finely built, sleek rather than stocky.
Redpoll bills contribute to this impression, being shorter and thinner than those of house finches. Though redpolls are quite capable of handling sunflower seeds, they’re rather more comfortable with something smaller, such as thistle.
So much for the similarities. How about differences?
There are many in both habitat and lifeways.
The redpoll is a country bird. The house finch is an urbanite.
The redpoll is a northern bird, circumpolar, in fact. Redpolls bred across the northern latitudes. House finches only recently have adapted to climates such as ours. They are native to the American Southwest. Caged house finches were released in New York City 80 years ago, and they’ve spread northwestward.
Today, house finches are residents here, present throughout the year. Redpolls, on the other hand, are visitors that never remain to breed.
Redpolls are what birders call “irruptive.” This means they show up in some years and not in others.
The critical variable is thought to be the seed crop in the taiga, the scrub woodland belt that circles the globe at high latitudes. The common trees in this area are birch and spruce. When these fail to produce seeds in abundance, the redpolls move south.
This has not been a good redpoll year.
At the feeder set up in my backyard west of Gilby, N.D., the first redpoll of the year showed up about 10 days ago. So far this winter, I’ve never counted more than five at the feeders. This is in sharp contrast to “irruption years,” when the number of redpolls in a migrating flock might number several hundred, or perhaps more.
Redpolls are active and energetic birds. Figuring how many are in a large flock is, put plainly, purely guesswork. The biggest flock I’ve ever seen was in an unharvested field of sunflowers within the Icelandic State Park Christmas Bird Count Circle. This is about 100 miles northwest of Grand Forks. I reported 500 birds. There might have been twice that many, perhaps even more. The rule on bird counts is to underestimate, rather than exaggerate.
Redpolls present another challenge: There are two kinds.
The hoary redpoll is lighter than the common redpoll, and it appears rather flat-faced. In our area, hoary redpolls are much less frequent than common redpolls, by a ratio of — I’m guessing — as much as 50 to one. This is imprecise, of course, because the birds flock together and sorting out redpolls is a difficult under the best of conditions.
Identifying these two species can be intimidating. The best clue is in the name, hoary redpoll. “Hoary” is an old-fashioned word most familiar to us in the phrase “hoarfrost,” which describes an accumulation of frozen water vapor on tree limbs, power lines and other exposed surfaces.
The name is apt when applied to redpolls; the hoary redpoll is lighter in color than the common redpoll. It appears — well — frostier.
In Eurasia, the hoary redpoll is usually called “Arctic redpoll,” which conveys a different notion but is still an evocative name.
Scientists aren’t fully satisfied that there are only two species of redpolls. Some specialists suggest there are as many as six.
Of houses finches, however, there is one species only.