Subject: Re: Interesting Behaviors
Date: Jan 2 10:50:21 1996
From: Dennis Paulson - dpaulson at ups.edu


Mike Waller wrote:

>This past week I observed a couple of interesting behaviors that I haven't
>been able to find in any of my reference books.
>
>2. Eared Grebe swimming with a female Common Goldeneye in the inlet and
>diving a split second after the duck. The grebe stayed within a few feet of
>the duck for over an hour on the first day and they were seen again the
>following aftenoon. They would dive come up and stay on the surface for
>10-15 seconds and dive again. Each time the grebe diving a split second after
>the Goldeneye. At onme point they became separated and the grebe appeared
>almost almost frantic searching for the duck. Once found the grebe swam to
>the duck and resumed station three feet astern, and diving in sync.
>
>Any thoughts?

I haven't a clue about the sparrow. By "spinning" do you mean in a
horizontal plane, i.e., reversing its stance to the opposite direction on
the branch?

About the grebe. I wrote a note about this phenomenon (Commensal feeding
in grebes. Auk 86: 759, 1969) after observing Horned Grebes feeding with
Surf Scoters here in WA and Least Grebes feeding with domestic ducks in
Costa Rica. It's actually a very common phenomenon, and I have seen it
many many times since. Watch flocks of Surf Scoters where Horned Grebes
occur to see how often you see them together, and that they often do the
same thing you described. Presumably while foraging for invertebrates, the
duck disturbs fish that the grebe can capture. Eared Grebes eat a lot of
invertebrates as well as fish, of course.

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416