Thursday, May 6, 2010

Woodcock intrigue

My earlier video post of the two American Woodcock at our Croft Preserve in Goshen has spurred quite a few responses and I thought I'd share some of people's insights as well as the results of some additonal research today.
The synchronized "Woodcock Walk" shown in the video is a known behavior in these birds and apparently this is how they wander through the woods. However, WHY they do this is still a mystery.
When observing these kinds of social interactions, several questions arise: why is this behavior taking place & who is involved? In this particular case the interaction could be territorial (two males competing over prime real estate or the most desirable female); it could be a courtship behavior (a male and a female interact and may mate afterwards); or we could be looking at a parent/chick interaction. Due to the pronounced size difference between the two birds, the first option does not seem very likely as two competing adult males would be expected to be of comparable size. As for the other two options, the jury is still out but leaning towards the latter option.
There is a pronounced sexual size dimorphism in American Woodcock and females are considerably larger than males -- in extreme cases the female can be more than twice as heavy as the male -- so a ritualized courtship behavior has not been ruled out entirely. However, the fact that the larger bird vocalized after being separated from the much smaller individual and was visibly agitated because of this separation, hints at the fact that it was a parent trying to re-connect with its offspring. As was mentioned in a previous blog post here American Woodcock along the shoreline are currently still found sitting on eggs or caring for downy young. Apparently, at the same time, older (2-3 weeks judging form the bird's size) young are already moonwalking in the northwestern hills. Woodcocks have a protracted breeding season and the timing certainly works out.
So, even if we are watching a parent bird crossing a road with its single young (note that American Woodcock usually lay 4 eggs) the question of WHY still remains...
Many cryptically colored animals will persist their cryptic behavior even when they are placed in an environment that makes them highly visible (on many occasions I have seen bright green snakes sit really still, pretending to be invisible, in the middle of a tan dirt road, even when you walk right up to them). Perhaps this is happening here also and it is irrelevant to the birds that they are in the middle of a paved road: they simply walk like this regardless of their surroundings...
Another question that was brought up today is whether this behavior is innate (genetically encoded and present when the chick hatches) or learned from the parent(s). I don't think anyone has an answer to these questions -- I certainly have not been able to find any clues in the literature. Regardless, this is certainly a nice reminder of how much we still can learn about creatures that we share our environment with. Even if we never figure this one out we'll at least have a nice excuse to admire birds with some pretty slick moves!

Thanks to all who contacted me with information about Woodcock and their behavior!

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