Michael,

"Persistence" may be a behavioral variable subject to evolutionary
interpretations. The animal is perhaps "programmed" to break off the
attempt when the cost/benefit ratio of continued efforts decline below
what may be expected at the next "patch"?

Gene Hunn (hunn at u.washington.edu)


On Wed, 24 Aug 1994, Michael Smith wrote:

>
> Hi Tweeters,
>
> I had another thought about jaegars, one which I brought up in my last
> posting, but failed to discuss, as I thought it was already too long.
> But I think the term 'persistence' certainly applies to jaegars as well.
> When the old routine of 'following the researchers to rob nests' fails
> (like when we would catch them doing it), these birds would resort to
> robbing eider mothers of their broods. I recall on one occasion a
> Parasitic who dive-bombed a female Spectacled Eider who was hiding all of
> her chicks underneath her wings. This jaegar went on for at least twenty
> minutes before I lost interest and had to move on (sorry, I don't know
> the outcome). I think in many cases their refusal to cease and desist
> results in a good meal. Another curious phenomenon, though is the close
> association of eider nests to jaegar nests. The eiders actually seek out
> their enemies nesting sites because the jaegars defend a large territory
> from other critters like gulls, snowy owls, and Arctic foxes. They also
> have the nice character to not eat the birds nests within these
> territories. The down-side of course is that when the young hatch, mom
> has to get them safely out of the jaegars territory, without them being
> eaten. So there are costs and benefits to that scenario as well. All in
> all it's a dog-eat-dog world out there, or at least a bird-eat-bird world.
>
> Mike Smith
> University of Washington
> whimbrel at u.washington.edu
>