>Now I find it very hard to believe that the terns and gulls are getting enough
>return on the energy invested in catching these ants to make it worth while...

>It is watching behaviors such as this that have always made be very suspicous
>of these nice, neat bioenergetics theories that explain all bird feeding
>behaviors.

Hmmm...of course, an argument from incredularity is no proof that they're
not getting enough return on the energy invested in catching these ants to
make it worthwhile.

For starters, possibly it isn't the number of calories gained vs. expended,
but perhaps the ants are particularly rich in a particular nutrient(s),
no?

>I agree that if this was a regular occurrence evolution would provide some
>mechanism to work against it but if it is an occurrence that happens relatively
>infrequently, why would it even be noticed from a behavioral evolutionary
>standpoint?

Predation, injury - each of events need only occur once in an individual's
life to cause the end of it. Frequency of an activity, in itself, is
no measure of the impact it has on reproductive success.

Besides, apparently it is a regular occurance - it happens every year,
he says.

>OK Tweeters, is there some chemical in ants that drives birds to such excess?

Ahhh...I see you've been having similar thoughts. I don't know the answer,
but it seems like the right sort of question to be asking.

Though, the quote you included only contained an OPINION that the
energy gained was less than the energy expended, so it is seems
reasonable to ask if this assumption is really true.

After all, I could jump up and down for a quite awhile for a Dove
Bar before expending the calories contained in one. And I'm not
particularly skinny!

- Don Baccus, Portland OR <donb at rational.com>
Nature photos, on-line guides, at http:://www.xxxpdx.com/~dhogaza