>Maybe it's just that birds have the option of simply flying
away to
>alternative habitat when conditions get too bad???
Hi Harvey
It could be as simple as that I agree! But in other alpine
areas of the world, birds have evolved to occupy specialised
alpine niches. In Australia it seems that at least summer
alpine resources/niches are vastly under-exploited by birds
though. So even though the lack of alpine endemics seems
fair enough, the small number of resident and/or migrant bird
species using the area in summer still surprises me.
L.
Lawrie, Harvey
What is the geographical history and age of these areas? I wonder if
there has been time for bird speciation if these areas were
ice-covered in the last glaciation. The mobility of birds can slow
down speciation - population fragmentation is much more likely for
small mammals and reptiles; barriers to dispersal which are important
for a pgymy possum would be invisible to (say) a honeyeater - esp. as
the birds that would first occupy these habitats will be apated to
following patchy and seasonally varied resources anyway.
I agree this does not explain the under-utilisation of the resources.
Could facultative alpine species have failed to make to make it
through the glaciations? ie would there have been alpine habitat
available, just more northerly, or at lower altitudes, than those
habitats currently exist. Or did this habitat type shrink altogether
in glaciations. If the later, that might explain under-utilisation as
well as the lack of endemics.
Kim
Until April 2002 visting at
Division of the Humanities and Social Sciences
101-40
California Institute of Technology
Pasadena, California 91125
USA
phone: 626-3953608
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