For the western European flyway, when the Ice Age came the migratory
birds continued to migrate, but each year they had to migrate a
shorter distance, until by the height of the Ice Age they were
probably migrating from Central Africa over the enlarged Sahara, to
Northern Africa. When the ice retreated they gradually increased their
migration distance again. As the range contracted so did the
population, when the range increased again, the popualtion increased
again. What we are seeing now is the potential habitat for migrants in
Europe (and in Africa), and suitable habitat en route is being lost,
,and so the popualtion is declining, thought without the contraction
in migratory range.
The picture for the eastern European flyway is more complicated, I guess.
John Leonard
On 02/05/2008, Lindsay & Diana Nothrop <> wrote:
>
> The colder weather leads me to less twitching and more philosophy. In that
> vein of thought by the fireside, I noticed an article in last Saturday's
> Canberra Times (page B3) lamenting the decline in migratory birds in
> Europe. This follows Prof Richard Kingsford's recent similar lament over
> rapidly declining numbers in Australia. The CT article postulated that this
> was leading towards extinctions (and so we should all feel terribly guilty
> and will sorely miss our Latham's Snipe).
>
> The decline in migratory bird numbers of course is due to a convergence of
> Hillary Clinton's presidential campaign, the Taliban resurgence and a rock
> star for an Environment Minister as we all know - and possibly climate
> change as well.
>
> What I tripped over though was the statement that ".. after millions of
> years as one of the most spectacular shows in the natural world, the
> Afro-European bird migration system is going fundamentally wrong".
>
> "Millions of years" ??? The last ice age ended just 8000 to 10 000 years
> ago. Northern America and Europe were covered a mile deep in ice and the
> rest of the UK was a barren wasteland devoid of all fauna and flora
> according to a web article. All life forms in the UK arrived in extremely
> recent times geologically speaking.
>
> There was no bird migration to northern summers then. With all life
> confined closer to the equator, there would have been little seasonal
> effects. So what happened? Why are all long-distance migratory birds not
> extinct already?
>
> Did the birds put their migratory desires on ice for a few thousand years? -
> I think not. Did the migratory habits evolve since the ice age? - I think
> not as the time is far too short in evolutionary terms. Did they just
> adapt and if so why cant they do it again but for different reasons?
>
> Is there another explanation?
>
> Lindsay Nothrop
>
>
--
John Leonard
Canberra
Australia
www.jleonard.net
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