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Re: Little skulls...

At 04:44 PM 10/21/99 -0700, dbensen wrote:
>>>>>It is not *that* quickly.  The papers suggests tens or hundreds of
>thousands of years, if not longer.  It is probably due to relaxed
>selection, allowing accumulated mutations to decompose the defensive
>behaviors.  Indeed there may even be selection *against* some of the
>defensive behaviors, to the extent they reduce reproductive efficiency in
>the *absence* of cuckoo eggs.<<
>How do we know it's taking place if it takes thousands of years?
As I mentioned before - it is largely inference, combined with some current
reactions to habitat alteration by humans.

The pattern of nest selection in NA cuckoos is regionally, and even
*locally* variable, and the foreign-egg-rejection response in potential
hosts is also variable between populations of the same species.  The
particular way in which these two traits co-vary is suggestive.  Also,
changes in exposure of potential hosts to cuckoos is having some strong,
and in some cases alarming, effects on some species.
May the peace of God be with you.         sarima@ix.netcom.com