The flight display of the male American Woodcock has to be one of the most remarkable avian performances in the world. And yet, despite the fact that countless ornithologists and birders have marveled at this spring spectacle, some very basic questions are still unanswered, including this one:
- Are the sounds entirely mechanical (produced by the wings) or are some vocal sounds included?
There is now general agreement that (at least) most of the sound is produced by the three outermost primaries, which are unusually narrow. Presumably air rushing between them produces a whistling sound. This can be heard year-round whenever a woodcock is flushed, the wingbeats produce a rapid trill similar to the takeoff sound of other species like Mourning Dove.
Most of the flight display involves a steady twittering sound like the takeoff sound but continuous for twenty seconds or so as the bird climbs several hundred feet. As the display progresses, and especially during the final seconds as the bird descends rapidly, the woodcock produces a much more intricate and complex series of sounds, with loud clear chirps interspersed among the twittering. It is these loud chirps that are said to be vocal sounds and not produced by the wings.
You can listen to an audio recording of the flight display from Virginia on Xeno-canto.
I can’t find the source of this bit of information. An authoritative account by Pettingill in 1936 states (without comment or citation) that the chirps are vocal, and this is repeated by every study since then, right up to the BNA account in 2013. But none of them cite a source. Ever since I was a kid, hearing woodcock displaying in Connecticut in the 1970s, I have marveled at and wondered about the sound. I came to the conclusion years ago that all of it must be produced by the wings, and was surprised to read recently that the chirps are still thought to be vocal.
All I can offer to support the idea that these are wing sounds (not vocal) are a few circumstantial points:
- the pitch and quality of the chirps is similar to the normal wing twitter, just an enhanced version
- There are no reports of chirps, or any vocalization resembling these chirps, being heard from a woodcock on the ground or in low flight; only during the flight display, and mainly in the steepest and fastest descent. The known vocalizations of American Woodcock are all lower: gruff, croaking, or buzzy.
- the chirps are interspersed among the twittering sounds in the display, but never overlapping any of those. If the chirps were vocal, I would expect them to overlap some of the twittering, instead they perfectly fill the gaps between tweets
- chirps are produced during the descent at the end of the display, and coincide with certain abrupt movements as the bird swoops back and forth, as would be expected for a wing noise
The chirps do sound a bit out-of-place in the display, and I can understand the thinking that they are vocal, but to me the evidence favors wing sounds. If the claim that the chirps are vocal is really nothing more than “conventional wisdom” passed down through the decades, then I feel more confident that these are in fact wing sounds.
Given that the display is only performed in near-darkness, high in the air, and at high speed, it will be difficult to resolve this question conclusively. This is just another example of the mysteries that still abound, even with some of our most familiar and well-studied birds.
Pettingill, Jr., O. S. 1936. The American Woodcock Philohela minor (Gmelin). Mem. Boston Soc. Nat. Hist. 9:169-391. link
McAuley, Dan, Daniel M. Keppie and R. Montague Whiting, Jr. 2013. American Woodcock (Scolopax minor), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: link, subscription required