The mysterious sounds of the American Woodcock

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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?
American_Woodcock_wing
The spread wing of a male American Woodcock, showing the three modified outer primaries that produce a whistling sound in flight. Immatures and females have slightly broader outer primaries, and presumably make a slightly different sound.

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.

American_Woodcock_final5secs
The final five seconds of the display flight of American Woodcock, showing the compex arrangement of chirps (tall vertical slashes) and twitters (short high notes). Notice that all of the chirps are perfectly and regularly inserted between the twittering notes.

 

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.

References

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

3 thoughts on “The mysterious sounds of the American Woodcock”

  1. Pingback: Blog Birding #231 « ABA Blog

  2. Hi David,

    I measured some woodcock feathers in a wind tunnel a few years ago while working with Rick Prum at Yale. When analyzing their feathers I assumed only the twitter was non-vocal, and that the chips were vocal.

    Comments on your points:

    1) To me, the pitch of the sounds you call out is not similar because the chirps are frequency modulated (FM), and FM sweeps are fairly rare within feather-sounds. But that said, in a wind tunnel, the woodcock feathers are capable of producing a range of frequency of sounds from (if I recall correctly) 4 KHz to 10 KHz, which is a substantial range. The range in the tunnel does not necessarily correspond to the range of sound produced by the bird, due to differences in airflow.

    2) there are plenty of vocalizations that are only uttered in highly specific contexts, especially in sexual displays, so the absence of similar calls in other contexts is not particularly strong;

    3) birds (e.g. the hummingbirds I study) routinely time their vocalizations with motions, so it would not be surprising for these vocalizations to be made only when the bird is not making the wing twitter; lack of overlap is not strong evidence;

    4) This is the best evidence these sounds are non-vocal. Are the wings flapped distinctly differently than during the regular twittering? I haven’t seen this display when I lived on the east coast, and would love for someone to get some video. I remember reading somewhere that they can be spotlighted when displaying, so it should be possible to get video. HSV cameras can record IR and they do make IR spotlights, so it would be possible to illuminate bird with light it can’t see. In my opinion, the strongest criterion for diagnosing a non-vocal sound is whether there is a strong correlation between the kinematics (motions) and the sounds.

    All that said, the chirps sound vocal to me. It’s going to take positive evidence to convince me otherwise.

    -Chris Clark

  3. David,

    I too have marveled at the woodcock sky dance over a lifetime. Have banded males on their singing grounds since the 1970s.

    I ran across this piece on hummingbirds today.

    “Another close encounter…

    “One of the most extraordinary of hummingbird facts relates to the courtship ritual of the Anna’s hummingbird.When he sees a potential mate, the male Anna’s hummingbird will fly up to 130 ft in the air, then dive to the ground at an alarming speed, around 88 ft per second! To put this into perspective, the force of gravity exerted on the bird’s tiny body at this rate of acceleration is equivalent to that which would cause near loss of consciousness in fighter pilots performing a high-speed banked turn. Even stranger, these little birds don’t just perform the move because it looks impressive. It also sounds great, as the wind on their tail feathers creates a chirping sound on the way down”

    Wow! I look at the hummingbirds at our feeders and watch their tail feathers – minature versions of a woodcock’s.

    I now believe the male woodcock’s chirping on his descent is caused by its tail feathers.

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