When I was 18, I hitchhiked to Chicago, where another teenaged birder, Joel Greenberg (now a famed author and naturalist), had promised to show me a Henslow’s Sparrow. On a chilly June morning, we visited the beautiful Goose Lake Prairie. Later I wrote a poem about the day; it began like this:
A breezy norther chilled the blood, as little sun was shining.
We slogged across the sticky mud of field and marsh combining,
While all around us, Henslow’s Sparrows laughed, and stayed in hiding,
Eluding birders with their craft, and freaky kids deriding …
I won’t bore you with the rest, but this fragment conveys a couple of points: Henslow’s Sparrows live in dense grasslands, and they are elusive creatures.
Indeed, this sparrow has played hide-and-seek with birders for the last two centuries. It’s a specialty of the eastern states, with a breeding range (current and historical) extending from the Atlantic to the eastern Great Plains and a short distance north into Canada. It winters entirely in the southeastern states.
Within that range, its known breeding distribution has changed over time. In the early 20th century, Henslow’s Sparrows were locally common in summer along the Atlantic seaboard from New England south to New Jersey, but they’re now essentially gone from that region. In Ohio, they increased dramatically in the 1920s and ’30s but have declined since. In Kentucky, the expansion was noted later, from the 1940s to the ’60s. In the western part of their range, Henslow’s were first found nesting in Oklahoma in 1987, Arkansas in 1988, and North Dakota in 2001. States like Minnesota, Illinois, West Virginia, and North Carolina have seen big increases and declines in the past.
Habitat is the key. For nesting, Henslow’s Sparrows require areas of tall, dense grass with a thick dead grass layer on the ground, scattered wildflowers, and standing dead stems, but no trees. Within this cover, the sparrows stay down out of sight except for singing males, which will perch at the top of a weed or a dead stalk barely above the top of the grass. The song is a shockingly simple tsslick!Males will sing at any time of day and even all night.
The birds also seek out dense habitats in winter in the Southeast. Open savannahs with scattered tall pines and an understory of grass or sedges may be ideal, but such sites must burn every few years. If they don’t, too much brush will grow for the sparrows’ liking. Pitcher-plant bogs are also favored sites. Needless to say, the birds are very hard to see in such places.
Despite their elusive nature, Henslow’s Sparrows are favorites with many experienced birders. Sometimes we even wax poetic about them. See the photos and captions with this article for details on how to identify this subtle creature.
What to look for
Size and shape. A small sparrow with a relatively large bill, large flat head, and short tail.
Overall color. Olive-green wash on face, contrasting with tones of rich reddish brown on the back and wings.
Face pattern. Distinct black mark set back behind (and separated from) the eye, and two very narrow black moustache stripes.
Pattern of underparts. A “necklace” of very thin, black streaks on buffy chest, and a few equally thin streaks on the flanks.
This sparrow was discovered in 1820 by John James Audubon, who described it to science and named it for the British priest and naturalist John Stevens Henslow. Apparently, Audubon never heard the bird’s song. He didn’t miss much. Many North American sparrows have complex and beautiful songs, but Henslow’s Sparrow achieves fame for having one of the simplest and worst. The song is distinctive enough once learned, however. Territorial males usually take an exposed perch while singing, providing the best chance to spot and study this elusive creature. Like related species, Henslow’s Sparrow seems to put a lot of effort into its modest vocal output, throwing its head back and opening its bill wide to deliver a simple tsslick!
Seen up close, the lack of strong markings around the eye gives Henslow’s Sparrow a blank expression; a very narrow white eye-ring is seldom noticeable. The black triangular mark behind the eye is conspicuous but unconnected to other marks, and two very narrow black moustache streaks are also isolated on the plain face. A pale stripe through the center of its crown is seldom obvious. Thin black streaks arranged across the buffy chest seldom or never come together into any kind of dark central spot. The streaking on the chest helps to separate Henslow’s from the adult Grasshopper Sparrow, but beware that juvenile Grasshoppers are strongly streaked, and even some adults have dark streaks at the sides of the chest.
Very similar to Henslow’s Sparrow in shape and behavior, the Grasshopper Sparrow is much more numerous and widespread. It’s another grassland species, but it seems far more adaptable, occurring in a wider range of open fields, including much drier sites than those used by Henslow’s. On Grasshopper Sparrow, the face is mostly buff, not olive, usually with a bright yellow spot in front of the eye. It shows hardly a hint of dark moustache streaks, and only faint streaking at the sides of the chest, so the lower part of the face and the underparts are much less marked overall than those of Henslow’s Sparrow. A narrow white stripe through the center of its dark crown is often noticeable.
An uncommon specialty of the northern Great Plains in summer, wintering mainly in grasslands of Mexico and Arizona, Baird’s Sparrow is unlikely to overlap with Henslow’s except perhaps during migration. Related to Henslow’s and Grasshopper Sparrows, it’s similarly large-billed, flat-headed, and short-tailed. Best field marks for Baird’s Sparrow involve the colors and pattern of the head and chest. Its head is washed with ochre yellow, contrasting with the whitish throat and chest. Its crown is finely streaked with black, with a gap in the middle revealing a yellow stripe, and the black moustache streaks are thick and obvious. Its back and wings lack the strong reddish brown tones usually shown by Henslow’s and Grasshopper Sparrows.
An elusive nomad
Henslow’s Sparrows have changed their distribution over the long term, as land-use practices have altered the landscape. But increasing evidence suggests that individuals move around from year to year, or even within a single season, more than most birds.
In a recent study, Mark Herse and others, working out of bird ecologist Alice Boyle’s lab at Kansas State University, did thousands of point-count surveys across eastern Kansas throughout two nesting seasons. They found Henslow’s Sparrows at 98 sites, but only four of those sites were occupied in both years of the study. Furthermore, even within seasons, the birds often changed locations. At three-quarters of the sites where Henslow’s were found, they were recorded only once.
This nomadic behavior is an adaptation to the changeable nature of their habitat. Birds of mature forest can use the same territory every year, but Henslow’s Sparrows favor an early stage in the natural succession of habitats. When a plot of land in eastern North America is cleared, it will grow back up — first to a grassy field, then to a brushy meadow, and eventually to forest.
Henslow’s like the early stages — dense fields of tall grass, which are maintained only by frequent cutting or fires — so as their favored sites grow up to thickets or get mowed down, they have to move on to fresh fields. By staying loose and mobile, they can take advantage of new sites quickly.