I've seen this behavior several times as well. A couple of times there
have been hundreds of Shovelers swimming in a large compact circle. It
seems like an effective means to stir up shallow areas for feeding. I've
also wondered when there are large groups of Shovelers in this feeding
frenzy, where is the most advantageous place in the feeding flock (at the
center? on the periphery?).


David Buckley----------------------------------------------------------------
lsdb at u.washington.edu
West Seattle, USA