It’s a still, muggy July morning, and I’m on the hunt. When the ear is the hunter’s tool of choice, the warm and humid air provides excellent conditions for the transmission of sound waves. I’m standing on a hilltop in an 18-acre prairie bordered on all sides by woods but with unrestricted views to the north. Beams of sunlight escaping through the eastern tree-lined edge are highlighting the yellow flower patches of early sunflower, prairie coreopsis and compass plant, and the white flower patches of wild indigo and wild quinine. My eyes lift from the colorful flowers to the far vista of Wisconsin’s picturesque Driftless Region countryside of steep, wooded, rolling hills and deep, open valleys. I close my eyes, leaving all of this visual stimulus, and wait for my quarry to reveal itself.
The repetitive sound of a cricket makes it to my ear first, followed by the “bouncing-ball” trill of a field sparrow to the south, and a “dick-dick-cissel” song of a dickcissel to the west. Also to the west, but well into the woods, I hear the haunting flute-like song of a wood thrush. The fleeting drone sound of a passing bumblebee fades into the “squeaky door” song of an indigo bunting. The morning is alive with nature sounds; my brain races to separate each sound and link it to its creator.
I hear the soft sound “tsi-lick.” Excited, ears straining to confirm, I hear it again. Yes, I think, I have found “heard” what I’m looking for – the Henslow’s sparrow!
The Henslow’s sparrow looks like, well, any other sparrow. Its soft, insect-like song can be hard to detect and easily confused with an insect call. The bird is so secretive that it’s hard to see even if one knows its general location by honing in on it from its call. In my experience, I visually locate the male sparrow in about a third of the times I hear them calling. The birds spend nearly all their time in the grassy duff layer and scampering on the ground, rarely flying higher than just over the top of the vegetation. Their habitat consists of open grasslands with a dense litter (thatch) layer and no, or very few, woody plants present.
Because of large-scale habitat loss, prairies and grasslands, this little guy is in trouble. It’s listed as endangered in seven states and Canada. The Wisconsin DNR lists the sparrow as threatened. The Henslow’s sparrow is listed in The North American Bird Conservation Initiative’s (NABCI) “2016 State of North American Birds’ Watch list,” which includes bird species that are most at risk of extinction without significant conservation actions to reverse declines and reduce threats.
The Henslow’s sparrow continues to call for a few more minutes before falling silent. For seven consecutive weeks now, I have heard this little guy calling from the same general location. This bird has caught my attention because of the habitat he has apparently claimed. The 18-acre prairie with its big-sky view to the north is certainly large enough for a few Henslow’s sparrows to occupy. The “structure” of the prairie is also right with its thick grasses and no woody vegetation. What is missing, however, is the thatch or litter layer. This prairie was burned in the spring consuming all of the previous year’s vegetative thatch! Vegetative thatch, or litter, is a critical component of the Henslow’s sparrow habitat needs, according to scientific literature and from my field experience.
To date, I have witnessed Henslow’s sparrows re-occupy prairies after extensive woody control and partial rotational burning. But this is the first I have consistently located an “apparently” breeding male bird calling from a thatch-free, recently-burned prairie! Anyone else have similar observations they would like to share?
The relevance of this observation is that more habitat would be available to Henslow’s sparrows should they adapt to breeding in thatch-free grasslands. Grasslands used for hay could be used for breeding if the first haying is delayed until mid-summer. Many planted prairies, burned in their entirety for a whole host of reasons such as safety, financial and time resources, lack of habitat knowledge and government program regulations, would now be available to breeding Henslow’s sparrows.
We have the knowledge to save the Henslow’s sparrow. I have seen the proof in conservation measures put in place by concerned landowners across southern Wisconsin. I fear, however, that the scale of our successes (in terms of restored habitat) are too small to reverse the decline of this unique and secretive little sparrow.
Maybe nature, in spite of our lack of collective effort, will find a way for the Henslow’s sparrow to adapt? Or maybe it’s just wishful thinking?