Expert: Roger Lederer - 1/13/2010

Question
QUESTION: We live near a small lake in Colorado.  We've noticed that in the winter ducks on this lake gather in groups of two to twenty or so and swim in a counterclockwise circle.  Do you know why they do that?

ANSWER: Without knowing more than what you told me, I can only guess that they are trying to keep that part of the lake from freezing up.

---------- FOLLOW-UP ----------

QUESTION: The ducks only do this in winter so your explanation about keeping the lake from freezing makes sense.
Any idea why the motion is always counter-clockwise?  There is a video of this at http://video.google.com/videoplay?docid=8112690528797127090#

Thanks.

Answer
Well, again, without knowing the exact circumstances - size and depth of lake, surrounding habitats, species of duck, other bird species on or near the lake, etc., I can't give you a definitive answer. However, it is known that some bird species show a "footedness" - that is, left or right handedness. But it is not consistent. It apparently depends on the bird that is most influential in the group that decides which direction the flock will circle.