We recently received a note from one of our dear readers, Nancy, from Southport about a special bird sighting that she experienced on March 31. This is what she wrote:
“I went out on my deck, morning cup of Joe in hand and did my usual perusal of, what I refer to as, the bird playground/ restaurant, on my side lawn. All was fairly unremarkable that morning until I scanned over to the damp, dirt driveway area, just in front of my garage. I looked and looked, trying to determine if I was seeing a small dug up pile of gravel or a misplaced duck-shaped, beautiful caramel-colored friend. One thing that kept me interested was that the ‘mystery matter’ began to move in a back and forth rocking motion! I moved slowly and quietly back into my house—this urgently became a binocular moment! I shared my discovery with my Mom and she posted herself in the window for observation. Upon closer look, I became concerned with this very unusual rocking motion. My first thought was that the ‘duck?’ was in distress as the rocking appeared almost like a panting motion. At this time, I discovered the extremely long, narrow beak. This was no duck.”
Nancy was right. It was not a duck! Her email goes on to describe how she eventually deduced that it was a newly arrived American woodcock. A member of the family of birds that includes the sandpipers, yellowlegs, sanderlings, and other so-called shorebirds, the American woodcock is one of the most secretive. While many people have heard the buzzy “peent” sound of the male at dusk in spring as he works to attract a female, few people have actually ever had a good look at one.
So it’s no wonder that Nancy didn’t immediately recognize the woodcock in her yard—getting a clear view of one in broad daylight is not a common occurrence. Nancy’s observation of the rocking motion of the bird as it stalked away into the woods is astute and highlights a peculiar behavior of the species that has been written about and its motivations debated for years. Bowdoin College trained ornithologist Olin Sewall Pettingill (who we wrote about in a past column) wrote a paper in 1936 that included mention of several hypotheses about the woodcock’s rocking behavior.
Some ornithologists conjectured that the rocking motion observed in both American woodcock and its Old World counterpart, the Eurasian woodcock, could be a way to cause ground vibrations that would bring earthworms to the surface for capture or allow the birds to hear or feel the earthworms move. Perhaps this was suggested because certain small gulls and plovers have been seen to vibrate the legs when standing in mud. That behavior was thought to stir up small invertebrates that the bird could then capture and eat. Others thought the woodcock rocking was done to make the bird more difficult to observe because it would mimic moving shadows when a bird was in a wooded setting. This may be an idea that comes from the observation of bitterns that sway slowly back and forth when spotted—a behavior itself that has been attributed also to the idea of providing camouflage by attempting to move with wind-blown reeds in a marsh.
Pettingill, in his 1936 paper, suggested that the woodcock rocking movement was what he described as a “nervous action resulting from fear or suspicion.” More recently, scientist and author Bernd Heinrich built on this idea with his hypothesis that the rocking motion was a way for the bird to signal to a potential predator that it had been spotted and therefore fruitless to attempt to pursue it. It’s an interesting hypothesis and one that, if true, might explain some of the other odd behaviors we mentioned like the swaying of bitterns and maybe even the leg vibrating of plovers and gulls.
Or it may be that woodcock rock for some completely unrelated reason that no one has yet imagined. Such is the wonder and mystery of the natural world!
East Machias video on snow: https://www.youtube.com/watch?v=EV2-ZCpoLi4
CLO video showing rocking motion and feeding: https://www.allaboutbirds.org/guide/American_Woodcock/media-browser/476033
Jeffrey V. Wells, Ph.D., is a Fellow of the Cornell Lab of Ornithology. Dr. Wells is one of the nation's leading bird experts and conservation biologists and author of “Birder’s Conservation Handbook”. His grandfather, the late John Chase, was a columnist for the Boothbay Register for many years. Allison Childs Wells, formerly of the Cornell Lab of Ornithology, is a senior director at the Natural Resources Council of Maine, a nonprofit membership organization working statewide to protect the nature of Maine. Both are widely published natural history writers and are the authors of the book, “Maine’s Favorite Birds” and “Birds of Aruba, Bonaire, and Curaçao: A Site and Field Guide” from Cornell Press.