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Note on the Woodcock Rocking Display
Bernd Heinrich*
Abstract - Scolopax minor (American Woodcock) is well-known for its crepuscular foraging, nuptial
sky dance, and concealment by both cryptic coloration and immobility. It occasionally engages in a
highly conspicuous rocking motion that has been interpreted by some as a strategy for worm-hunting.
However, the literature on this behavior, combined with current observations and theory, can instead
more plausibly be interpreted as an advertisement of unprofitabi lity.
Scolopax minor Gmelin (American Woodcock, hereafter Woodcock) is a woodland
bird of eastern North America (Bent 1927, McAuley et al. 2013, Mendal and Aldous 1948,
Sheldon 1967) that commonly feeds on earthworms. It is best known for the male's aerial
display (Longcore et al. 1996). While walking, Woodcocks sometimes shift their body up
and down and forward and back with each step, while maintaining their head steady. This
rocking behavior, which is also reported for Scolopax rusticola L. (Eurasian Woodcock;
De Forges 1975, Severinghaus 1978), has been described as a means of foraging for earthworms,
although various alternative hypotheses have been proposed for it as well.
The worm-hunting hypothesis for the rocking walk apparently originated from Bent
(1927), who mentioned that “it [the Woodcock] is said to beat the soft ground with its feet
or wings, which is supposed to suggest the effect of pattering rain and draw the worms to the
surface.” His only support for this idea is reference to C.J. Maynard, who had in 1896 observed
a captive Woodcock which “stamped with one foot, giving several sharp, quick blows,
after which he would bend its head near the ground and then listen” before catching a worm.
Subsequently Christy (1931:14) observed Woodcocks in Pittsburgh, PA, in August on lawns,
gardens, and parks and concluded that “most of the bird’s movements were very deliberate”
involving “peculiar pressing movements of the feet—and I gained the distinct impression
that the angleworms were located by the sense of feeling through the feet.” But Pettingill
(1936:269) conjectured instead that the behavior is a “nervous action resulting from fear and
suspicion”, and Worth (1976:374) proposed that it may mimic either moving leaves or act to
reduce detection by “minimizing shadows”. Marshall (1982) observed these rocking movements
of 2 Woodcocks in early spring in suburban St. Paul, MN. Because his observations
were, like Christy’s (1931), on lawns under overcast sky on apparently wind-still days, he
excluded Worth’s (1976) idea of the birds’ mimicry of either moving leaves or shadows.
Marshall’s (1982) observations were made in early spring when “the frost line varied
from 5 to 20 cm in depth.” Furthermore, on his second observation after 15–20 cm of fresh
snow had fallen, the Woodcock were “very conspicuous as they rocked, whether on snow,
lawn, or leaf litter.” It was therefore unlikely that the Woodcock were either stamping their
feet to cause worms to come up out of the ground, or to hide. Unable to find a plausible
explanation, and despite his strong evidence against it, Marshall (1982) nevertheless concluded,
“I would suggest that a minute movement of earthworms close to the surface in
response to the slight changes in pressure from the rocking bird’s foot, allows the Woodcock
to detect them by sight or perhaps by an infinitesimal soun d.”
Bent (1927) included observations of Dr. Robert Cushman, who described a Woodcock
leaving her nest and spreading her tail “to show full advantage [of] the double row of
*PO Box 153, Weld, ME 04285; bheinrich153@gmail.com.
Manuscript Editor: Glen Mittelhauser
Notes of the Northeastern Naturalist, Issue 23/1, 2016
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glistening white spots at the ends of the double row of retrices and under coverts. Next,
flashing this striking banner slowly, she would move off among the trees in the attitude of
a strutting cock, stopping when we refused to follow, and then tripping ahead a few steps,
all the while bleating softly. The effect was astounding: the ordinary low visibility of the
Woodcock against the forest floor no longer held, for the spotted fan became a most conspicuous
and arresting mark.”
In certain situations, some animals make themselves highly conspicuous to predators, as
a defense. Alcock (2013) summarizes these deliberately conspicuous behaviors, such as the
stotting 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.
In the spring of 2011, I observed the rocking display of Woodcock near Weld, ME, at the
edge of a hill-side clearing by a stand of Acer rubrum L. (Red Maple) and A. sacharum Marshall
(Sugar Maple). The clearing had been used as a Woodcock spring display area for at least
the last 30 years. The Woodcock were at the lower end of a slope in a level area between the
maple trees and several Viburnum dentatum L. (Arrowwood Viburnum) and Ilex verticillata
(L.) A. Gray (Winterberry) bushes. At the time of the observations, the leaves and grass in that
area were conspicuously marked by dozens of white blotches of bird scat, hence indicating
previous presence of the birds. On 25 April 2011, I flushed 1 Woodcock from the area and a
second started to walk away from me, taking slow small steps, and, after each step, rocking
its body back and forth in the typical and often-described rocking walk display. I remained to
watch this bird for about a half hour. Whenever I followed it in a slow walk, it continued its
rocking motions as it walked keeping about 6–10 m ahead of me. It stopped when I stopped,
and resumed its rocking walk display when I again drew closer to it.
I returned to the same water-soaked, unfrozen, fecal-marked area in both the early and late
afternoon of 9 May 2011, and a Woodcock was there each time. It again did not flush, and I
again followed the bird. As before, it rocked up and down in place, or backward and forward
during its walking in the typical rocking behavior. It occasionally accentuated this display by
also flaring its tail, prominently flashing white feathers up and to the sides (described as the
“tail flare” alarm by Morgenweck and Marshall [1984]) and as previously described by Bent
(1927). After 10 minutes, I withdrew ~100 m to climb 10 m into a Red Maple tree to hide behind
its trunk and watch the bird with binoculars. During my 40 minutes of watching from a
distance, the Woodcock ceased its display, and did not vocalize.
Since the fecal markings indicated that Woodcock had spent considerable time feeding
at this location, potentially on worms in or on the open, wet ground, I searched and discovered
several earthworms under the wet leaves on top of the water-saturated soil. The worms
were not moving and did not respond to my handling them. The hypothesis (Christy 1931,
Marshall 1982) that the bird(s) I was watching were, by their rocking display, attempting to
activate worms to come to the surface at near 0 °C seemed suspect.
The Woodcock’s rocking-walk behavior was noteworthy because it seems to violate the
usual cryptic behavior of individuals of this species when approached by humans or dogs,
when the birds usually flatten themselves to the ground which they often resemble and
where they often remain until flushed into flight after being approached closely. Throughout
October 2015 (when Woodcock were on migration), I attempted, with the help of 2
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assistants, to find Woodcock and again observe this rocking display by searching forests
within 300 m of my 25 April observations. We flushed Woodcock on 15 occasions, but were
never able to detect one before flushing it. Even when we were about 2 m from birds, they
always flushed before we saw them, flying about 50–80 m before either settling back onto
the ground or departing out of sight. However, we flushed 2 of the birds 3 times in succession
and the openness of terrain allowed us to see where they landed. When we approached
them the second time they flew up when we came to within 4–5 m from them, and the third
time we approached the same individuals they flushed at a distance of 8–10 m. Although
knowing where these transients had landed, we were still unable to see them before they
flushed. Apparently these birds’ lack of the rocking walk display was associated with their
being in their normal habitat where they could escape detection by hiding, but they were
willing to leave any area within it. The only 2 fecal spots found indicate that the site was
only a temporary one for these birds.
The Woodcock rocking-walk observations by Christy (1931) and Marshall (1982), and
those by Cushman quoted by Bent (1927) had been made under conditions that contradict
the worm-hunting hypothesis. Furthermore, the rocking up and down and back-and-forth
movements could arguably be judged as either gentle or forceful, but not the kind designed
to cause earth vibrations. Furthermore, the above-quoted rocking-walk display from Bent
(1927) closely approximates the “tail flare” alarm signal (Morgenweck and Marshall 1984),
which the rocking walk of the bird I was following at times exhibited. It was likely an accentuation
of the rocking display, just as the flushing of Woodcock from increasingly greater
distance after greater pursuit was likely a sign of greater alarm. It is especially noteworthy
that the Woodcock exhibited the rocking display precisely when the potential threat came
near, and stopped abruptly on my withdrawal to watch from a distance through binoculars.
Given those behaviors and sequences of events, the worm-hunting hypothesis is contradicted;
no animal proceeds to forage the moment it senses it is being stalked.
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.
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 va lue to the bird.
Conversely, to secure the alternative worm-hunting hypothesis and distinguish the incidental
from the causal would require proving all of the presumptions that would make
the behavior work: proof of buried worms, confirmation of their moving in response to a
Woodcock’s rocking walk, proof of a Woodcock’s ability to sense these movements when
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they occur, the Woodcock’s responding to these movements by probing there into the
ground, and lastly then also locating the worms. Earthworms can indeed be caused to come
up out of the earth by vibrations. In Florida's Apalachia National Forest, people have for
generations harvested a large endemic earthworm (Diplocardia mississippiensis Smith) by
driving a stick into the ground and vibrating it and the soil mechanically by power tools,
historically using a model T Ford, and now chainsaws (Catania 2008). These vibrations
may mimic falling rain or digging by moles and elicit the worms’ escape response (Catania
2008). However, the walking by Woodcocks are unlikely to cause such vibrations.
Since no strong evidence for the rocking walk as a worm-hunting strategy exists, it
seems premature to call the worm-hunting hypothesis an established “fact”. Another hypothesis
which may illuminate the function of the Woodcock’s fascinating behavior is at
least consistent with available facts. As per the discussion by Alcock (2013) of the conspicuous
signals given by prey to potential predators, this behavior is in accord with the theory
of advertisement of unprofitability, to prevent said predators from pursuing the alerted prey.
Acknowledgments. I thank Craig Neff and Pamelia Markwood for showing me a video
clip of a Woodcock; John Alcock, Glen Mittelhauser, and an anonymous reviewer for helpful
comments and suggestions on a draft of the manuscript; and Lynn Jennings and Joshua
Brown for Woodcock flushing.
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