Date: 12/18/17 10:54 am
From: James V Remsen <najames...>
Subject: Re: [LABIRD-L] American Woodcock foraging behavior
John et al. — the predator-signalling hypothesis has the fewest problems as far as I can see, especially with observations like yours of the rocking behavior when obviously not foraging. The other two shorebirds that have stereotyped movements presumably analogous to this, e.g. Spotted and Solitary, are also solitary foragers, and Spotted in particular feeds in exposed situations. Likewise, the two waterthrushes, both inveterate bobbers, are solitary water-edge foragers. In all of these species, the head remains conspicuously motionless, thus maximizing chances of detecting a predator. So, there’s a common dominator that might reveal the cause.

Another hypothesis I’ve found is that the rocking behavior is to disturb earthworms into moving, which then allows the woodcock's highly tactile bill (and hearing?) to detect worm movements. I don’t buy it because, as noted by John, they do it when not foraging. I also don’t see how the rocking creates worm-disturbing noise— better to just scratch ground with feet or poke it with bill.


===================

Dr. J. V. Remsen
Prof. of Natural Science and Curator of Birds
Museum of Natural Science/Dept. Biological Sciences
LSU, Baton Rouge, LA 70803
najames<at>LSU.edu

> On Dec 18, 2017, at 7:52 AM, John Dillon <kisforkryptonite...> wrote:
>
> One of my favorite birds because they're so peculiar and so difficult to observe.
>
> A few years ago, in the middle of the day, I was driving on a paved rural road in Claiborne Parish, and I found a woodcock in the middle of the road. It was walking across the road, bobbing, and obviously not foraging. I snapped a few photos but can't find them at present. Can't remember if I got video, but I think I did. My point is it was bobbing while walking across asphault and not foraging. Could have been foraging before and after, I suppose.
>
> I also can't help associating its odd movements with other odd bird movements, like tail bobbing. Here's a link to a note by David Sibley in which he summarizes a study on Black Phoebes that concluded that they bob their tails relative to the likelihood of a nearby predator. Could woodcock bob with a similar reason?
>
> http://www.sibleyguides.com/2015/03/why-do-phoebes-pump-their-tails/
>
> John Dillon
> Athens, LA
>
> Sent from my iPhone
>
>> On Dec 18, 2017, at 7:34 AM, Paul Dickson <Paul...> wrote:
>>
>> Labird: First, let me join the chorus of accolades for Van. Though I have watched woodcock a time or two, all that is of no value to anyone but me because I didn't carry away anything from those experiences but charged neurons. As he and other scientists often point out, recorded data is value in science. Look at how many people have already benefitted from his taking this video. Awesome.
>> On Jeb's question I happened to watch a snipe from my deer stand just this past Saturday as it fed along the slick mud bank of a ditch. I should point out that some of my past woodcock feeding observation was also from deer stands. Though few birders deer hunt, those that do realize what a great birding blind a deer stand is. The snipe did not bob as it fed. It walked and probed somewhat like woodcock but did not bob. Bobbing is movement and movement is dangerous to small meaty birds. Movement reveals prey to predators. Woodcock's constant bobbing must have a very valuable return to overcome the cost. The reason few people have seen it is because Woodcock stop bobbing when they sense a predator, such as a human. I have always thought, with no empirical data behind this opinion, that woodcock bobbing had to do with either of the species' two unique feeding parameters: forest feeding or nocturnal feeding. Recognizing that they feed, at times, in grassy water edge situations of open fields and mud flats, just where snipe do, then the forest is left as the unique single niche parameter but night-field feeding is still a unique combo. No other soil-probing feeder is nocturnal or forest feeding. Lastly, Woodcock are circumpolar (2 species) and several more species have radiated into Oceana so they have been in a lot of places for a long time, plenty of time to develop a unique feeding behavior suited to either forest or night. I did a quick search and found a video of a Eurasian Woodcock sort of rocking but not as pronounced and for the tropical Pacific island species, no information on this feeding behavior.
>> This is the most studied shorebird because it is a traditional game bird so there must be bountiful research on this bobbing behavior out there in academia but apparently no video as good Van's recent effort. They also have particularly weird version of the 'broken wing' display when protecting chicks. (nope, no video of that, haven't seen it in the iPhone era)
>> Paul Dickson

 
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