Re: MODERN BIRDS AND MIGRATION

[Betty Cunningham <bettyc@flyinggoat.com>]

It's also likely that tradewinds will affect migratory behavior-if it's
easier to fly long distances via a high altitude tradewind, you might
not find migratory animals travelling out of this 'byway'.  
You might try checking this theory if idyllic spots that are not along a
byway are bypassed for those that are, even when further away.
However in the case of fossil birds I have no idea how you would try and
identify mesozoic tradewinds.

-Betty Cunningham

Matthew Troutman wrote:
('cause David asked)
> <<Thirdly, is it known or is there a good theory as to why birds migrate
> in the way they do? The Godwits migrate vast, distances, for example,
> from Northern Europe to New Zealand. Why so far? If it's just food or
> water there's plenty of that a lot nearer than New Zealand. Migratory
> behaviour is predictable, regular, systematic, in fact, highly evolved.
> Are there many species that travel similar distances to the Godwits, or
> are they unique?>>
> 
> Long migration distances in birds is certainly not unique amoug
> vertebrates (or even animals).  So far, the best theory (in my opinion)
> is that long migrations are charged by the changing seasons in temperate
> zones and at the poles.  Moving away from birds for a second, look at
> the variation in spring and summer habitats for North American/South
> American vespertillonid bats.  Some individuals stay near Panama,
> whereas others summer as far north as near the Artic Circle!  It all has
> to do, probably with how their ancestors migrated, because a bird or bat
> seems to not be able to migrate without doing so with its parents and/or
> "flock".  As for long distances travelled by terns and godwits, it was
> probably a gradual trend for some individuals to travel far North and
> South.  Another factor might be certain individuals or flocks watching
> other individuals for flocks.