Wednesday, April 14, 2021

Nature’s Ways … Snowbirds — our winter visitors from the north

Most people associate fall bird migration with birds leaving Pennsylvania to head south. However, a few species fly south to spend their winters in the Keystone State. Some of these, such as the snowy owl, common redpoll or red-breasted nuthatch, do not visit every winter. Others, such as the dark-eyed junco, fly here from Canada each fall by the millions — and that number is no exaggeration.

Juncos are far from an endangered species. The Cornell Lab of Ornithology estimates the total junco population at more than 630 million birds.

If the name, “dark-eyed junco,” does not ring a bell, you may simply know them as “the snowbird,” because many people begin to notice them when the first snow covers the ground. If you own an older field guide, you might not even find the dark-eyed junco listed. The juncos visiting Pennsylvania used to be called slate-colored juncos — a unique species.

In 1973, the American Ornithologists’ Union decided to group five (then separate species) of juncos as a single species — the dark-eyed junco (Junco hyemalis). Our slate-colored variety is now considered a sub-species of the dark-eyed junco. Slate-colored juncos are the only sub-species in the eastern United States.

Juncos are actually sparrows and they are about the same size as the house sparrow — 5.5- to 7-inches tall. The male junco looks like a white bird that has been turned upside down and dipped in grey paint. The top half of its body is a medium to dark grey color and the bottom half is white.

Juncos are not often seen except when they are feeding on the ground under bird feeders. Early in the fall, the most common junco sighting might be a quick glimpse of several birds flitting from the cover of one shrub to another.

Even then, they are easy to identify, because when they take off, both sexes display distinctive white outer tail feathers. As they fly away, they look like small grey birds with two vertical white stripes on their tails.

If you watch juncos carefully, you will notice that they are hoppers, rather than walkers — moving across the ground by taking short hops. Juncos scratch the ground looking for food, and another thing that sets them apart from many other birds is that they scratch with both feet at the same time. Wild turkeys, for example, scratch with one foot at a time.

Juncos usually feed below established birdfeeders — cleaning up seed dropped by other birds. They prefer oil sunflower seeds and millet. If you want to attract more juncos, scatter additional seed on the ground.

Juncos have another interesting feeding adaptation. They sometimes land on fragile stems of grasses — bending the plant to the ground — where they then eat the seeds. Other species only feed by landing on stems that will support their weight.

It is unusual to see one junco alone – juncos travel and feed in groups. While participating in the Christmas Bird Count on New Year’s Day 2013, I counted more than 85 birds in just one group. During the 2020 Christmas Bird Count, juncos were again the most frequently seen bird — we counted 137 on our route in the Marsh Creek Valley. Within a flock, juncos have a well-established pecking order, with dominant birds often chasing the less dominant members of the group. Females are usually subordinate to the males.

Just like cardinals, our slate-colored juncos are sexually dimorphic (male and females colored differently). Females are more brown than grey. The ivory-colored bill of both sexes is often tinged with pink.

An understanding of their sexes is another thing that has changed about our knowledge of juncos. In central Pennsylvania, it is common to see flocks composed of almost all grey-colored birds, with maybe just a few brown ones mixed in. As a result, it was assumed that brown was just a color variation of grey, rather than sexual dimorphism.

Research on juncos has helped ornithologists to learn that, when moving south, the birds separate by age and sex. In the east, young male birds only fly to southern Canada or the New England states. Mature males fly farther south into Pennsylvania, and most females migrate all the way into our southern states. This is an interesting observation, but at this point the answer to a more important question — why does it happen? — can only be speculated. “These patterns may result from the birds’ need to strike a balance between surviving the winter and getting back to the breeding grounds in the spring,” David Sibley wrote in “The Sibley Guide to Bird Life & Behavior.” “Birds wintering in the south are subjected to a less stressful winter, but birds wintering farther north can return more quickly to the breeding grounds and may get the best territories.”

Male juncos locate and defend territories, and that could explain why males winter closer to their breeding grounds. Another related explanation might be the subordinate role of females in the winter flock. Female birds do not fare well in mixed-sex flocks because the males will drive them away from the food. According to Sibley, they may move farther south to escape the males. Each fall, shortly after hummingbirds depart for warmer climates (mid-to-late September), I usually see my first “snowbird.” It is difficult to say when juncos arrive in Centre County because they stick to brushy habitats. As their numbers grow, people are more likely to notice them, particularly when there is snow on the ground.

I do know that I saw my first junco this past fall on Sept. 28. Juncos nest in Canada, although small numbers of juncos will stay in Pennsylvania all year. In fact, a few nest as far south as the mountains of South Carolina. When they nest in Pennsylvania, it is like-ly to be in the wooded northern-tier counties or anywhere with a more northern-like climate. Several years ago, I saw a nesting pair of juncos in Tioga County in mid-May, but I have never seen this locally. This small grey bird is not as flashy as a cardinal, not as noisy as a blue jay, and not as friendly as a chickadee. Nonetheless, the dark-eyed junco is a very interesting and welcome winter visitor.