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Tuesday, January 28, 2014

Rhythm and Blues, or Rumba?

This might be a firsta post without a picture or an audio file!  But I have to share this video.  It made me laugh out loud, and I hope it does the same for you.  And even though this is an eastern bird, there *is* a California connection in fact, a very local one!  First the video (and then come back and read more):


I've seen American Woodcocks (Scolopax minor) moving like this when I lived in Massachusetts.  But I hadn't seriously looked into whether anyone had researched the unusual motion.

After watching the video, I started reading about it and noticed a reference to this paper:

Marshall, W.H.  1982.  Does the woodcock bob or rock and why?  Auk 99: 791-792. 

Perfect.  I downloaded the paper and was shocked to see that the author, William Marshall, lived on Oakmont Drive in Santa Rosa, CA!  William Marshall observed woodcocks in Minnesota and described the motion like this:

"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."

He argues that the motion should be called rocking rather than bobbing or teetering to distinguish it from the motions of American Dippers or Spotted Sandpipers.  

And he summarizes four possible reasons that various authors have proposed for the rocking: 

(1) it's a "nervous reaction resulting from fear or suspicion" Marshall discounts this theory as the birds he observed were undisturbed and birds that he did see in disturbed situations did not exhibit rocking (but see #4 below).

(2) it's mimicry "of leaves being moved by a breeze" — Marshall discounts this theory because when there isn't a breeze, rocking makes the bird conspicuous; and leaf motion is more erratic and jerky than this rhythmic rocking of the woodcock.

(3) it's mimicry of "prevailing shadows" — Marshall discounts this theory because there were no shadows when he observed the rocking behavior.

(4) it's movement used when feeding — Marshall believes that pressure from the woodock's rocking foot may cause a slight response from earthworms, allowing the woodcock to detect them by sight or even sound.  He also suggests that it's possible this rocking motion initially developed for feeding may also reveal itself in stressful situations (such as being in open landscapes exposed to potential predators).

It's interesting to think about this last possible reason for the rocking motion and then to watch the video again (or just to watch it again to laugh some more).  I can see what he means by there being pressure on that front foot.  And if you've ever seen plovers "foot-trembling" on the mudflats, there are some possible similarities there.  It's just that woodcocks do it while walking, rather than while standing in place!

If you're still with me, I can't help but add one more thing.  Marshall quotes all of the different ways this rocking behavior were described in the past.  Although the video used a Rhythm and Blues tune (Tequila by The Champs), an author in 1958 said the woodcock walked in a "rumba-like manner."  Which do you think is a better match?

P.S.  I'm guessing the author who proposed the woodcock moved in a rumba-like manner was thinking of Afro-Cuban rumba, not ballroom rumba.  For one example of the former:


P.P.S.  Thanks to Blair for sending the woodcock video!


Claudia said...

I laughed too! The thing that strikes me about the motion is that it's fore-aft. (I think of "rocking" as side to side.) I'm not sure we have a word for what the bird is doing. (It's like the difference between striped and banded). How about a new term: the sway-bob?

One difference between our bird and Marshall's description. Most of the time our bird lifts and then replaces each foot before continuing.

One thought about the feeding explanation. It seems like the bird wouldn't need to move it's body that much just to place it's feet properly. Why all the exaggerated body bobbing? Does it need to throw its weight into it? Put enough pressure on the ground for the earthworms to feel it?

I'm going to vote for "rhythm and blues rumba" as the best match. (Isn't Tequila a combo of the two? It was perfect).

That was a fun post!

John W. Wall said...

I've never seen that behavior in that bird, but it does remind me of watching dippers and wondering if there's any advantage to their dipping motion. FWIW, I posted a short video of a dipper working Lagunitas Creek: http://vimeo.com/36056337