StemCell Therapy

I have not yet seen any redpolls at my feeder this year, but it is only early February, so a birdwatcher can hope. When they do arrive, I dont plan to stress out about which species and subspecies are present. Because, frankly, it is difficult to tell them apart, and they are all adorable.

Poll is a Middle English word that means head. It is still occasionally used in that sense if you are talking about livestock. Polled cattle are the unhorned members of a breed, which is to say, they are just headed. Of course, we most commonly use the word to mean either a place to vote (going to the polls) or a collection of votes (taking a poll). This probably derives from the fact that people have only one head, but they have two hands. So, in a crowd it is safer to count heads to get an accurate count, as there are always jokers who will raise both hands.

Both the male and female redpolls have a prominent scarlet square right on top of their heads, while only the males have the blush of pink or red on their chests and sides. Hence, this is a cleverer name than, say, the rose-breasted grosbeak, which leaves out the female entirely.

Most sources recognize two species of redpoll, usually referred to in this country as the common and the hoary redpolls. In Europe, the hoary is called the Arctic redpoll. Both adjectives are accurate, more or less. We use the word hoary infrequently. Generally, we intend it to mean having a frosted appearance. Hoar frost is the kind of frost that grows in obvious crystals, like icy fur on objects. Hoar is an Old English word that means appearing to be old. Several animals and plants with a frosted appearance get this tag: the hoary bat, the hoary marmot, and hoary verbena.

Hoary redpolls have a more limited breeding range than do common redpolls. The Europeans might do better to call them tundra redpolls because they only live in that habitat. In contrast, the common redpoll breeds in the tundra, but it also nests down into the northern taiga of Canada. Hoary redpolls, for example, breed only around Ungava Bay in northernmost Quebec, but common redpolls build nests halfway down the province and on Newfoundland as well.

The appearances of the two species follow at least two ecogeographic rules. Glogers rule states that endothermic species (warm-blooded) will be darker colored in more humid environments. In terms of the amount of precipitation it gets, the Arctic tundra is a desert, so that the hoary is a lighter plumaged bird than the common fits.

The sides and back of the common are heavily streaked with brown. This is especially pronounced in the females. In hoary redpolls the females retain some streaking, but it is very faint in the males. David Sibley includes an illustration in his page for the hoary redpoll that shows its absence of streaking under the tails as well. Common redpolls show variable amounts of streaking there.

The hoary also tends to be larger than the common, which conforms to Bergmanns rule: animals found in colder climates tend to have larger body mass than those from warmer climates. Common redpolls average 5.25 inches long, while hoaries average 5.5 inches, which isnt much of a difference. But the Greenland subspecies of the hoary averages a full 12% larger than the Canadian race. This constitutes what is called a cline, a gradual morphological transition across an environmental gradient. From the southern subspecies of the common redpoll in the taiga to the Greenland subspecies of the hoary, there is a tendency toward larger size in a progressively colder climate.

The cline does not apply as well to Glogers rule; the Greenland subspecies of the common is darker than its southern subspecies. But it works for the rest of the subspecies of both species.

The redpolls may even conform to Allens rule, which states that animals from colder climates tend to have a smaller surface-to-volume ratio (i.e., they are rounder) than those from warmer climates. This is often expressed as having smaller or shorter extremities. One of the characters used in the field to distinguish the hoary from the common (when they are both at your feeder in a single flock) is the smaller, shorter, straighter bill of the hoary.

On the New Hampshire Birds online forum, Fred Sladen of North Sutton recently shared a taxonomic discussion from the Illustrated Checklist of the Birds of the World (2016) that posits a third subspecies for the common redpoll. The so-called lesser redpoll is considered a longer- and slender-billed variant of [the] nominate with slightly longer wing and tail, and slightly deeper pink in adult male. To conform to the ecogeographic rules this subspecies should live somewhere warmer (longer bill, wings, and tail, Allens rule; and darker color, Glogers rule). In fact, it lives in northern Siberia, a colder, drier place than northern Europe, where the nominate species is found in Scandinavia, Finland, and the Baltic countries.

The redpolls were until recently in the genus Carduelis, a once species-rich taxon that molecular genetics has revealed to be what taxonomists call (when no one is listening) a garbage can group. Their DNA has shown the redpolls to be isolated branch of finches deserving of their own genus Acanthis, which is a name that was originally given to a Greek bird that now cannot be identified from contemporary descriptions of it.

The moral to this story is that when redpolls show up at your feeder, dont worry if you cant tell the species apart, never mind the subspecies. Their songs are the same and their ranges grade into one another, so its a mystery as to how they can tell each other apart.

Bill Chaisson has been a birdwatcher from the age of 10. He is a former managing editor of the Eagle Times and now works and lives in the town of Wilmot.

See the original post here:
Of a Feather: When cousins are two of a kind - eagletimes.com

This entry was posted on February 7, 2021 at 3:52 am and is filed under Molecular Genetics. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. |