Wayne Weber wrote:
> I have always assumed that the reason coots typically aggregate in
> dense flocks in the winter is for protection from predators--
> especially Bald Eagles. On Okanagan Lake in south-central B.C., where
> many thousands of coots winter each year, Bald Eagle attacks on coots
> are frequent (and frequently successful). Coots, unlike ducks, are
> slow to take off and are not agile in the air, preferring to escape
> aerial predators by diving. Gathering in dense flocks seems to give
> them some protection from eagles, in the same way that formation of
> dense flocks helps to protect Dunlin from Peregrine Falcons and other
> raptors.
>
Is that true? A big raft of coots presents a wonderful target for an
eagle--a raft of fresh meat it can dive at with a high probability of
hitting something. But an isolated coot is less visible and presents a
smaller target; an eagle would have to dive at it repeatedly to have the
same chance of catching it as it has of catching one random coot out of a
flock. Big flocks of shorebirds provide mutual protection because the flock
moves quickly and reverses direction quickly, with a confusing flashing of
wings, though I admit that such a flock also presents a large target. I'm
just suggesting that the issue isn't simple and requires some careful
analysis.

On the other hand (there's always another hand), if forming huge flocks
weren't adaptive in some way, coots wouldn't have evolved this behavior.

Burt Guttman
The Evergreen State College 360-867-6755
Olympia, WA 98505 guttmanb at evergreen.edu

Reunite Gondwana

> -----Original Message-----
> From: Grant Hendrickson <granth at halcyon.com>
> To: Tweeters <tweeters at u.washington.edu>
> Date: Sunday, December 03, 2000 1:53 PM
> Subject: Coot Behavior
>
>
> >Recently Gene Hunn wrote
> >
> >"I've been checking the waterfowl action on the north end of Lake
> Washington in Kenmore and Lake Forest Park of late. There's 2000 to
> 3000 water birds here regularly, 95% of which are coots."
> >
> >At the north end of Lake Sammammish there are hundreds of coots
> rafted up. This occurs each fall. Can anyone help me understand why
> they form these large groups at this time of year?
> >
> >Grant Hendrickson
> >Redmond, WA
> >granth at halcyon.com
> >
>