On the other hand vagrancy may not be an "adaptation" to anything, but
rather the result of chance misdirection due to the less than perfect
predictability of prevailing winds and the never perfect behavioral
programming inherited by individuals of a population.

Gene Hunn.

On Thu, 14 Dec 1995, Stuart MacKay wrote:

> Dennis wrote:
>
> > Whether the normal slow flux of bird ranges can deal with
> phenomena such as
> > global warming will be interesting to see. Birds should be able to
> > certainly handle it a lot better than salamanders, for example.
>
> Blackcaps (sylvia whatever - my bird books are all packed away)
> have dramtically shifted their wintering range in Europe in the last
> 15 years or so. Bird that used migrate south and east to winter in
> Italy have changed to south and west taking them into the southeast
> UK, The Netherlands, Belgium and France. Back home in northern
> Scotland we used to judge how good the autumn migration was by the
> number of "blackcap days" we had - sadly no longer. While not
> unusual there are hardly any to be seen in recent years.
>
> It is believed that local climatic change has been the triggering
> factor. Whether this is as a result of global warming is hard to
> say. However it demonstrates the resilience of some species.
>
> My personal musings are that vagrancy and reverse migration
> consigns / condemns a portion of the population to speculative
> migration. Should conditions in the species habitats start to
> change radically it may be possible that birds wintering or even
> breeding outwith their normal range may flourish. Whether it is
> genetic or a symptiom of genes is hard to tell.
>
> The blackcap is a good example of changes in wintering area. For
> breeding range changes, in the late 1970's and early 1980's there
> was a lot of colonisation of Scotland by species which used to breed
> in southern England as the European populations moved northeast.
> Red-backed shrike and wryneck in particular, though only wryneck was
> successful. In South Africa both swallow and common sandpiper
> (similar to spotted sandpiper) have started breeding - this is only
> 6,000 miles outwith their normal breeding range !!! They do winter
> there however.
>
> I think there are a few major surprises for scientists as the world
> starts to warm up. Personally I think that species will be able to
> deal with it - since they have undoubtedly been through it all
> before - however the rate of change will take a pretty significant
> toll, though I doubt it will lead to lots of extinctions that some
> people predict - ever the optimist.
>
> A good example of the staying power of species was shown in a
> recent edition of Science News. Apparently eggs of pond plankton can
> survive complete dessication for 2-300 years and successfully hatch
> once conditions become favourable.
>
> Makes ya think don't it !!!
>
> Stuart - T minus 17 and counting .........
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> Stuart MacKay - powered by NeXTSTEP
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>