Wild Side : Martha's Vineyard birders appreciate wintertime juncos
Photo courtesy of U.S. Fish & Wildlfe Service
We don't seem to get much snow any more on the Vineyard, but happily we still have "snowbirds." That's an old but appropriate common name for the small migratory songbird known more properly as the dark-eyed junco, Junco hyemalis.
A sparrow, but an atypical one, the junco's color scheme suggests a snowy day — flat gray above and white below. Females average paler above than the males, and all juncos sport white outer edges on their tails — a useful field mark for recognizing this species in flight. Long a personal favorite of mine, this bird is a widespread and fairly common winter resident on the Island, where it frequents thickets, weedy fields, and yards (especially yards with feeders).
Nearly a half-century ago, as my life-long interest in birds was becoming apparent, my scientist father guided me through my first simple study of bird behavior. For a half-hour or so each day, I watched the bird feeders in our yard, noting not just what species visited but where they chose to feed. After a few days, we compiled the results, and I remember my delight and amazement at the clear patterns that emerged. Goldfinches? Mostly at the thistle-seed feeder. Chickadees? A strong preference for whole sunflower seeds from a feeder just outside a window. And the juncos? (The species was known as slate-colored junco in those days.) Always, always on the ground.
A broader sample size would have yielded a slightly more complex picture! Juncos do sometimes eat directly from feeders elevated off the ground. And in wild settings, they often seek out seeds or insect eggs on the branches of shrubs (they seem to have a particular fondness for picking over birch catkins). But the results of that early experience in understanding bird behavior still ring true: juncos, like many of their sparrow relatives, are primarily ground birds, equipped and programmed to seek their food among dead vegetation at ground level. Like towhees, they often use a double-footed kick to churn up the leaf litter, exploring for the seeds that make up the bulk of their wintertime diet. And their pink bills combine the stoutness and dexterity needed to crush seeds and extract the edible contents.
The vast breeding range of this species extends from the Appalachians north into Canada and west all the way to Alaska. In New England, the junco is a nesting bird of the higher elevations, and during summer its song, a monotone trill like that of a pine warbler, can be inescapable in the mountains of Vermont, New Hampshire, and Maine. Relatively few breed in the Berkshires of Massachusetts. But in fall, juncos move south and downslope to winter across most the United States, generally occurring in small flocks and often associating with other types of sparrows.
The dark-eyed junco is one of those birds that inspires lively debate among ornithologists. As a result of the junco's vast geographical range, a number of quite distinct geographical races exist, some with accurately descriptive names like "pink-sided" and "white-winged." At various points in history, some of these forms have been treated as full species, though the prevailing sentiment is that interbreeding among forms is too extensive to support such taxonomic splitting. The current name "dark-eyed junco," then, subsumes five or six forms that were once considered species of their own. Even today, birders relish the discovery of a junco of a subspecies that doesn't belong here.
Juncos are not particularly shy birds, and if they are frequenting your feeding station, you can't miss them. But in more natural settings, their ground-hugging habits and drab coloration can make them hard to spot. Good cues to the presence of juncos are their call notes: a sharp "tick," which they seem to use to maintain contact with other flock members, and buzzy "zeet" that appears to function more as an alarm note. I can't think of any birds present at this season that have calls resembling these notes, so learning to notice junco sounds is a reliable way to locate this species. Juncos tend to be curious and a flock will often respond vigorously to imitations of a screech-owl call, popping up onto shrub tops to try to spot the predator. The presence of a real predator, such as a patrolling sharp-shinned hawk, will send a flock diving for cover. It is amazing how rapidly a chatty flock of a dozen juncos can utterly disappear.
Juncos are a wintertime specialty for Island birders, with the vanguard of the fall migration usually turning up in mid-September. Our wintering birds seem to thin out during April, but transients from farther south continue passing through into about the second week of May; some of these later visitors, approaching breeding condition, may give the trilling song of the species while they're here. Take some time to enjoy this species while it's here!