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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