Hello everyone,

Deb Beutler's observations reminded me of another note about group diving:

DesLaurier, J. R., and B. H. Brattstrom. 1965. Cooperative feeding
behavior in Red-brested Mergansers. Auk 82:639.

I can't seem to find my copy of this paper (I think it's around here
somewhere...), but according to another paper, it considered the group
diving in Mergansers to be a way of herding prey.

Perhaps this is what the grebes are up to (?). Yep, need to get that scuba
equipment! And if they are chasing something what is it? The prey can't
be too big if HOGR are catching and eating them underwater. I know that
the pelicans herd fish as well - as Deb and others mentioned.

It was interesting that Deb mentioned the gulls following - In the case of
synchronously diving Surf Scoters, Schenkeveld and Ydenberg proposed that
synchronous diving was a way of avoiding kleptoparasitic G-W gulls. Their
data showed that the scoters were more synchronous when more gulls were
around.

Enjoyed the grebe story too Deb! If only I knew what was going on in their
little grebe brains!

Bonnie Stout
Burnaby, BC
bestout at sfu.ca