Why do woodcocks rock when they walk?

February 28, 2021 • 9:30 am

First, have a look at these videos showing American woodcocks (Scolopax minor) walking. This bizarre way of walking (they do it only occasionally; see below), with a rocking motion and an absolutely steady head, is unique among birds. (People can’t resist putting this movement to music; turn off the sound if you don’t want to hear “Walk Like an Egyptian”!)

Juveniles do it as well:

Very young chicks also do it, though not as strikingly as the adults. Woodcocks eat earthworms and invertebrates (ants, millipedes, etc.) that they grub from the soil, and you can see this one probing a bit.

Finally, a range map from the Cornell bird site. If you live in the right place and are lucky, you might see one, though they tend to hunker down in the woods and become almost invisible:

 

I believe I showed a tweet of this behavior the other day and asked readers, “Why do they do this?”, noting that there are several hypotheses. I put the question to our expert ornithologist, Bruce Lyon of the University of California at Santa Cruz, who put me on to two papers (below), one of which may well have the correct answer. Let me add that we still don’t know the reason, and more observations and experiments are in order; but the one advanced in the second paper below makes the most sense given the data at hand.

Here’s the first paper, which summarizes several theories, but not the one that’s probably correct. It’s from a 1982 issue of The Auk (click on screenshot to read):

Marshall watched woodcocks intently—once for a total of 8 hours during three days in 1978—and describes the motion:

As the bird slowly walked about, its head and neck remained on a level plane, but its body was almost continually moving back and forth, best described as “rocking.” A line between the neck and dorsal feathers was obvious, because, while the body moved, the head did not. One foot was lifted high then placed down ahead with the weight on it; the other foot was lifted so that only the tips of the toes were in contact with the ground. This repetitious movement stopped when the bird picked a small worm from the surface, probed deeply to pull out a large worm, or extracted an insect from under a leaf. The head was well forward and held slightly to one side with the tip of the bill 3 cm or less above the surface.Sometimes progress was broken by repeated rocking in one place, and, less often, the bird stood motionless for several minutes.

He gives four explanations that had already been advanced at that time. The comments are mine:

1.) “A nervous action resulting from fear or suspicion”.  Given that this action calls attention to the bird, it would seem maladaptive to do this if there was a predator around. However, as we’ll see below, it may actually be adaptive in that situation.

2.) “Mimicry of leaves being moved by a breeze.” This seems unlikely as the birds do this when there is no breeze, as Marshall observes, and the rocking is not really very close to that of leaves, which move erratically.

3.) “Mimicry of prevailing shadows”.  As Marshall observes, they walk like this even when it’s overcast and there are no shadows, and the behavior, in fact, makes the birds more conspicuous, at least to a human observer, than when they stand still.

4.) Detection of earthworms or insects under the ground. The hypothesis is that the bird, by walking this way, exerts pressure on the ground that makes the worms and insects move, thus enabling the woodcock to detect them and eat them. At the time Heinrich wrote the paper below, 34 years later, this seems to have become the prevailing explanation. But, as we’ll see, it doesn’t seem likely. If you watched the first and second video above, you’ll probably see why.

Bernd Heinrich is a first-class scientist and naturalist, as well as a world-class long-distance runner, and I’ve read several of his books on corvids (he’s written a lot of popular books). This short paper, based on Heinrich’s observations of woodcocks, was published in Northeastern Naturalist (click screenshot to read the paper):

Heinrich’s observations show that woodcocks only walk like this under certain conditions: when they know they are being watched (Heinrich didn’t see them do it when he hid himself and watched with binoculars), and they do it in open habitat where it’s more likely that a predator would spot them. When Heinrich followed the birds, they rocked only when walking away from him. When he stopped, the birds stopped. When he started walking toward the birds again, the birds started their rocking walk.  Also, they don’t rock when they’re in the woods, where they’re more cryptic.

Although rocking, says Heinrich, occurs during foraging, it’s not likely that it helps the birds detect earthworms or other insects underground. For one thing, as you saw above, they do the “rock walk” on asphalt or on the snow, and there are no invertebrates to be found that way. Further, the way the birds walk is a gentle placement of the feet on the soil, and not, as Heinrich says, “the kind [of walk] designed to cause earth vibrations.” If that were the case, the bird would probably stomp forcefully on the ground, for violent vibrations are what make worms and insects move. (These are created in the American South by “grunters” who use a chainsaw to create violent vibrations in the soil to bring up worms for fishing.)

All of these considerations lead Heinrich to his hypothesis, which derives from observations of other animals that make themselves conspicuous to predators when they know predators are around:

In certain situations, some animals make themselves highly conspicuous to predators, as a defense. Alcock (2013) summarizes these deliberately conspicuous behaviors, such as the slotting of antelope (Pitcher 1979), the waving of the tail by an Anolis lizard when it had been discovered by a potential predator (Leal 1999), and the white tail flashing of fleeing Odocoileus virginianus (Zimmermann) (White-tailed deer), as “advertisements of unprofitability” that act to reduce the likelihood of attack by a potential predator. This hypothesis for the function of a potentially conspicuous behavior gives relevance to the visually conspicuous “rocking” behavior of Woodcock, given the circumstances of when it occurs and an anecdote of my own.

Here’s a springbok “stotting” (also called “pronking”), one of the behaviors thought to be an alert to predators saying, “Don’t bother to attack; I’ve seen you already.”

Why would an animal do this? And why would it deter predators? If a predator knows the potential prey has seen it, and has let it know that detection by a conspicuous display, it’s to the predator’s advantage not to attack, because its advantage of stealth has been lost. Attacking would likely be a waste of time and energy. And it’s to the potential prey’s advantage to make such a display, because it uses less energy to “rock walk” than, say, to fly away,= and potentially leave a spot rich in food.  The evolution of this behavior would probably start by some individuals doing something that makes themselves conspicuous when they see a predator, and those would be individuals in species that have the ability to flee successfully when a predator is close. But it depends on the display deterring the predator, so some learning of the predator must also occur. (Later, that learning could actually become an evolved behavior by the predator to simply not attack when it sees the display.)

And this is, my Best Beloved, is How The Woodcock Got Its Walk. Here’s Heinrich’s hypothesis:

I suggest that the Woodcock rocking-walk display is a response to what it perceives as a mild potential threat situation that is not severe enough to initiate predator-avoidance tactics to disrupt it into flight or cryptic hiding. The Woodcock’s rocking-walk display may act as a signal in a situation of a perceived potential audience or a predator, indicating that it is aware and can explode off the ground and escape if the predator seems likely to attack. The display saves the bird the energy and bother of flying off and possibly being chased.

The rocking walk display is likely to occur during foraging, because foraging is centered at a food-rich place that the bird may be reluctant to leave. In most instances, available video clips of the behavior (displayed on the Internet by interested citizens) were made of Woodcock in potentially threatening ecological settings or during a discrete threat. The Woodcock were either out of their usually preferred woodland habitat (Bent 1927, McAuley et al. 2013) or near humans and were thus potentially “nervous from fear and suspicion” as Pettingill (1936) had originally supposed.

Good scientist that he is, Heinrich proposes further tests, and (not shown below) also suggests tests of the “worm detection hypothesis”.

That the bird’s behavior while walking is variable, including a teetering motion, is undisputed, but the reason(s) for this behavior is still uncertain. To test the display hypothesis that I propose would require observing the bird unseen (perhaps by remote video camera), both undisturbed in its preferred habitat and then under the influence of a mild (but not strong) potential threat in the presence of a resource of significant value to the bird.

Here’s Bernd himself, studying his beloved ravens; I’ve met him once or twice:

Heinrich, born in Poland in 1940 (Wikipedia says Germany, but it’s wrong), is also an “ultrarunner”, and was the best in America at long-distance running during the first half of the 1980s.  He held records in the 100 kilometer race and in the straight 24-hour run (oy!), the latter with a record distance of 156 miles (he was then taken to the hospital). Here he is finishing the record 100K (62 miles!):

43 thoughts on “Why do woodcocks rock when they walk?

  1. Superficial comment: do these birds have an alternative name as do peacocks do : peafowl, or even peahen? I thought I’d ask since peafowl appeared in today’s great set of wildlife photos. I don’t know if there’s a reason for the alternate names. Wikipedia offers no suggestions.

  2. Woodcocks rock! Period.

    I noticed that as it walks/rocks, its head stays perfectly level and moves parallel to the ground. Perhaps its physiology requires it to rock in order to achieve that?

    1. No, birds have a remarkable ability to keep their heads rock-steady while their bodies to all manner of twisting and turning. I presume it’s because they need to stay focused on what they’re looking at while flying about or moving in other ways.

  3. Another superficial comment: after a 24-hour run I’d be walking like a woodcock, rocking on the spot and trying to take a step forwards…

    More seriously, Heinrich’s hypothesis certainly sounds plausible and strikes me as much better than the earlier ones.

  4. I did not know that the circumstances were so particular – that they rock especially when they know they are being watched. So comical as it is, the “don’t bother chasing me” hypothesis seems the best explanation best right now.
    They don’t bob, that’s for sure.

  5. I’ve never had the pleasure of seeing this behavior myself. I don’t see the woodcock until I’ve walked up on it and it has exploded into flight and nearly given me a heart attack.

    As for Heinrich, he’s an absolute delight to read. A Year in the Maine Woods, Summer World, Winter World, The Trees in my Forest, and for those interested in his life, The Snoring Bird. I don’t know what the full history of his birthplace is, but it’s currently in Poland, his Wikipedia page says Germany, but the link to the city say Poland, originally part of Pomerania, and it was occupied by Germany. So is it some sort of German/Poland cultural tug-of-war? I’d have to reread the relevant sections of the Snoring Bird again but he does talk about it and his family experiences during WWII.

    1. Połczyn-Zdrój was part of Germany in 1940 when Heinrich was born. It became part of Poland in 1945 after the Second World War when the Soviets took eastern Poland and gave a part of eastern Germany in return. The last time prior to that when Polzin was part of the Polish state was in the 14th century when Poland consisted of a number of fiefdoms with a king the dukes ignored.

  6. Hopefully in a few months mine will return: they are one of my favorite signs of spring. My husband was from New Hampshire, where they also call these woodcocks. In this portion of Vermont, they are called snipes. We had so much confusion over this in conversations (and arguments) that we finally agreed to talk Latin for all wild animals and avoid the problem. I still don’t know if we were talking about the same bird. Heinricih is one my favorite writers. I’ve read all of his books that I can get a hold of. This video of a woodcock (called snipe) is from April, 2008 and was through my window. Even though the video is primitive, you can see the movement she made while searching for food. She was there for a good 20 minutes.

    https://youtu.be/mPOOMOWhtJo

  7. “Heinrich, born in Poland in 1940 (Wikipedia says Germany, but it’s wrong),”

    His hometown was in Germany when Heinrich was worn. It went to Poland only in 1945. I am not sure what would be the correct country designation in this case, but Heinrich definitely born as a German citizen.

    1. I’m even more confused after flipping through The Snoring Bird. His father, Gerd Heinrich was born in Berlin Germany, he refers to his mother as Mamusha, as she was Polish. On his dad’s side (I think?) his grandmother is from a family that came from Germany to Poland who adopted a Scottish boy because they lacked a son, who when he grew up married a Jewish woman so his grandma was a Scottish/Jewish woman from a German family who moved to Poland, I think. She was given by her parents the estate the book calls Borowke, which is in Poland. Now, since his mother was Polish, and his dad was considered by the local SS as “polish friendly” they decided to travel far enough away from Borowke that she would not be known and pretend she was German and she and baby Bernd would be safe as part of the Lebensborn program, so he wasn’t from there, just born there, unless I’ve totally confused everything. I’ve certainly confused myself.

      Just go read his book!

      1. It is confusing! It helps to know that Poland did not exist as an independent country from 1795 until after WWI. So Heinrich’s mother was Polish by ethnicity, but possibly not a Polish citizen at birth, depending on whether she was born before or after 1918. Certainly his grandmother was not a Pole by citizenship, since the country didn’t exist.

  8. Not having learned about this until now, I had assumed the “woodcock jive” was just another funny bird mating ritual and/or a form of peacocking—“Look at me, I am so fit that I can bring attention to myself without getting eaten.” But obviously, if females and young’uns also do it then that theory goes out the window. The pronking explanation does seem like a good fit.

  9. I’ve never seen snipes/woodcocks displaying this behavior in Europe, but then my experiences resemble those of Christopher.
    I think that the pronking-like explanation (I’ve seen you and I’m superfit, you won’t get me, spare your energy) is the most probable one. All others do not appear likely at all, after reading the circumstances.

    I’ve been running the 100k several times in the 90’s, although I never came close to first. The deepest point is around 60 km, you don’t feel your joints anymore and the legs are heavy, and then you realize you still have a Marathon to run. I cannot imagine where the deepest point in a 24h race would be.

  10. Thank you for posting this article on the woodcock walk!

    My daughter Hannah and I love this bird, but so far we have only seem them (and mostly just hear them) after sunset when they do their courtship flights. Last spring she did a painting every day for the month of May, and the first bird she did to kick off the series was the woodcock: https://www.hannahjonesart.com/shop/timberdoodle. (Yes, they’re for sale, but I put the link just to show the drawing, which I’m rather proud of.)

    Maybe we’ll see one in daylight this year?

  11. Heinrich is indeed a great writer and a very smart guy with eclectic biological interests. He’s largely responsible for the application of questions and techniques from vertebrate ecological physiology to insects.
    He used to come (back) to visit UCLA occasionally when I was there, and he’d typically fly into LAX, change shoes, and run the 10+ miles to campus.

  12. Woodcocks, or Timberdoodles, have very recently returned to my home area of Appalachian southeastern Ohio. It is a regular practice of local naturalists, including myself, to go out at dusk to enjoy the male’s fascinating display flights. I am lucky in that they display and nest on my neighbor’s reverting to brush old farm, so I can see and hear them from across my fence. One of our first signs of spring, along with finding the Skunk Cabbage emerging in boggy seeps. These aerial displays can be readily found on YouTube. They of course nest here as well. Almost no nest structure, on the ground. I have banded two here over the years, an accidental capture when set up to band songbirds. Bernd Heinrich’s father served in the German army during WWII, as I recall helping guard railroad tracks from sabotage by resistance fighters. Heinrich graphically describes, in The Snoring Bird, their family flight westward as the Soviet forces advanced towards Pomerania. As holders of a fair-sized estate, part of the Junker class, the family certainly had a legitimate fear of being captured by the Soviet army.

  13. I’ve never seen snipes/woodcocks displaying this behavior in Europe, but then my experiences resemble those of Christopher.
    I think that the pronking-like explanation (I’ve seen you and I’m superfit, you won’t get me, spare your energy) is the most probable one. All others do not appear likely at all, after reading the circumstances.

  14. Interesting article. I can only say something on this part:

    Heinrich, born in Poland in 1940 (Wikipedia says Germany, but it’s wrong)

    That would be wrong. Wikipedia is more accurate. You could say “then Pommern (German Empire), now Poland” for instance.

    The region Pomerania was Prussia for centuries, then Prussia merged into the German Empire. Over older history, it changed hands many times and belonged to the (crusader) State of the Teutonic Knights, the Holy Roman Empire, Poland, Sweden, Denmark, and many even more specific terms. The NSDAP had their second best result in Pommern (Pomerania) in the last free democratic election.

  15. Thanks for that, PCC(E). Finding interesting items like that that I didn’t know that I didn’t know is what makes WEIT such a continual pleasure.
    And, of course, the quality of the comments adds to that.

  16. “Pronk” is an Afrikaans word meaning – more or less – “to show off”. Adding “-ing” to the word (to make a verb) turned it into a sort of English word.

    To see a sprinbok “pronk” in the wild is quite impressive. One can almost sense their joy to be alive.

  17. The body shifting of woodcocks and snipes may be in the same category as tail bobbing in other birds.

    Sibley says (https://www.sibleyguides.com/2015/03/why-do-phoebes-pump-their-tails/)
    “Lots of birds have a habit of pumping (or wagging) their tails. It’s mostly open-country birds like phoebes, wagtails and pipits, Palm Warbler, Spotted Sandpiper, and others. Many hypotheses have been suggested to explain why the birds do it, but nobody came up with an answer until Gregory Avellis in 2011.” (Avellis, G. F. 2011. Tail Pumping by the Black Phoebe. The Wilson Journal of Ornithology 123: 766-771.)

  18. On a related note, out west we have the American dipper, or Water Ouzel, which has similar strange behavior. It is an aquatic bird so one of the proposed explanations for its dips is “a form of communication in a noisy environment”. I have observed dippers for hours and I don’t think so. They do it even when there are no other dippers around. Looks to me to be a way of getting visual cues about the location of prey in the lake.

  19. Thanks for this great science post. What an endearing bird.
    Chameleons (don’t know if they all do or only some) also display this behavior while walking/climbing. Convergent evolution? Probably not.

  20. OK, I admit I read all the comments quickly, so please accept my apology if this point has already been made. I hate to be a killjoy, but even though there are very few natural moments as special as seeing Woodcocks walk (particularly special when mother and recently fledge chicks walk across a road, as I’ve seen) it isn’t unique. Just look at pigeons walking the next time you are in an urban park. What seems to be going on is the head is held very steady, unmoving relative to the ground as the body is moved forward, then the head catches up quickly, and the cycle continues. There are very few (any?) observers as careful and eloquent as Bernd, so I’m surprised if his comments don’t include this fact (and I missed them). I think the most parsimonious explanation is that they are keeping the head still to scan for danger, moving the body, then quickly adjusting the head. No need for detailed “explanations” of why there appears to be an endearing wobble. As for “rocking” during foraging, yes, but also during walking across a 2-lane paved highway, where there were no prey.

    1. First, a small correction: the movement is supposed to deter predation if the woodcock thinks a predator is watching, so your last sentence doesn’t make any sense.

      Both Bruce Lyon and I have watched videos of pigeons walking, and we don’t agree with you. Pigeons, while they bob during walking, do not stop during a walk and rock their bodies 6-8 times between steps like a woodcock does. Woodcocks are not at all like pigeons in that respect, and still appear to be an outlier. I’ll also quote Bruce:

      I took a look at the (woodcock) video, and while there are some similarities (holding head still while body moves) between pigeons and woodcocks (and for that matter coots when they swim and sunbitterns and egrets while they hunt), there are striking differences. I am pretty confident that there is more going on with the woodcock than with the pigeon. Pigeons are basically walking, while holding their head still for part of the walk. The woodcock is rocking its body back and forth several times without walking or moving. I think the signal idea seems pretty reasonable. I also think it is reasonable for people to raise doubts—and force us to think carefully about whether and how pigeon and woodcock movement differs—because it forces us to be more specific.

      Readers can judge for themselves by watching YouTube videos. Here’s one:

      It would help if you didn’t come off as thinking that you’re obviously right (“a killjoy”) at the outset.

  21. It’s because they heard the song Rockin’ Robin by Bobby Day and got jealous. Duh. (Although I do love any excuse to play Walk Like an Egyptian, so thanks for that second video.)

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