Wild Side: Elegant field sparrows

This small bird with a distinctive song prefers a woody habitat.

0
The song of a field sparrow is a series of clear, sweet-toned, descending whistles. — Laurie Sheppard, USFWS

I have a weakness for sparrows, those “little brown jobs” that are the bane of beginning birders due to their apparent absence of any real field marks. With practice, sparrows actually turn out to be fairly easy to identify (especially if you learn their songs and calls as well as their plumage patterns). And to my eye, the subtle brown and gray palette of this group of birds is quite attractive.

Perhaps the most elegant member of this group is the field sparrow, a rather pale and plain-faced sparrow with a reddish cap, unstreaked underparts (often tinged with pale orange), a stout, distinctly pink bill, and a clearly defined white ring around the eye. The song of this species may be its most distinctive field mark: an accelerating series of clear, sweet-toned, descending whistles. Once you learn it, this is a song you will never forget.

The field sparrow is not a common breeding bird on Martha’s Vineyard. I find nesting pairs annually in Correllus State Forest, but the number is always low; if I know of two or three pairs there, and we assume I miss as many as I find, there would be at most a half-dozen. I run into other pairs, or at least singing males, occasionally at other places as well; Waskosim’s Rock often has a pair or two, as does Menemsha Hills. But all in all, I doubt the Vineyard hosts many more than 20 pairs in a typical year. Although as a species the field sparrow appears reasonably secure across its entire range, I’d rate it somewhat precarious as a nesting species on Martha’s Vineyard.

In contrast to, say, the song sparrow, which is highly adaptable, field sparrows are constrained by quite specific habitat preferences for breeding. Nesting sites appear to me to fall into two classes. The first is low, shrubby habitat adjacent to a sharply defined woodland edge. The fire lanes in the State Forest fit this profile, with mowed strips of habitat framed by mature oak, or pine/oak woods. So do powerline rights-of-way, which are a common breeding habitat for field sparrows on the mainland. Birds using this type of setting probably nest in a thicket in the shrubby vegetation. But the males spend a lot of their time singing from halfway up a tree along the woodland edge.

The other setting this sparrow likes to nest in is old fields or pastures, still recognizably fieldlike but partially grown up with woody vegetation. A favored feature in this setting seems to be red cedar trees, a common colonizer of abandoned fields. The sparrows use these trees for both nesting and as singing perches. Patches of this habitat exist scattered around the Island, and nesting field sparrows sometimes turn up in them. On the mainland, one reliable place to find this habitat type is in the “leaves” of highway cloverleaf interchanges. Red cedar often gets well established in these bits of wasteland, and the ring of traffic around them makes these settings nearly immune to human intrusion. You can find a lot of field sparrows by driving slowly along highway entrance or exit ramps, with the car windows down so you can hear a song if it is given.

As scarce and localized as it may be on the Vineyard in the summer, the field sparrow is a regular and occasionally rather common fall migrant, sometimes lingering into or even through the winter. Sparrows in general can be quite gregarious in fall and winter, aggregating in modest flocks to migrate or forage in productive habitat. Flocks of migrant sparrows often contain a mix of species, and field sparrow may be in the mix. But field sparrows, more so I think than our other sparrows, also turn up in single-species flocks. These may be fairly large — once, on a Christmas Bird Count, I encountered a flock of around 30 individuals — but rarely seem to remain in one place for very long. As a result, birders tend to either miss this species entirely, or hit the jackpot, in fall and winter.

Very much a bird of the Eastern U.S., field sparrows nest north to roughly the Canadian border and south into all but the southernmost parts of the Gulf Coast, Texas, and the Florida peninsula. To the west, the range of the field sparrow stops where the plains hit the foot of the Rocky Mountains, and this species is a pretty good find for a birder in the Western or Southwestern U.S. More Western populations of field sparrow average grayer and duller than Eastern ones, a difference that some taxonomists feel amounts to two defined subspecies. I’ve occasionally found grayish birds here on the Vineyard; whether they are vagrants from the West or just grayish members of our typical Eastern population is impossible to say.

Arriving like clockwork around the third week of April, field sparrows are already getting established in their few strongholds on the Vineyard. It’s worth keeping an ear cocked for the distinctive song of the elegant little bird.