Joe Morlan

Crossbills are nomadic by nature with their populations shifting from year
to year and season to season. The birds move in response to changes in the
cone crop which is sporadic and unpredictable. Sometimes a good crop is
followed by an almost complete failure the next season. These failures
force the birds out into new areas in search of food. It is a strategy
that is built into their life history and required for their survival. In
view of this, it is not surprising that Red Crossbill occurrences in the
East Bay have been sporadic in recent times and I think this would be
expected regardless of climate change.

There is no doubt that climate change such as that during the Pleistocene
ice ages had a significant impact on the ranges and distributions of birds
and other animals. North America was quite a different place 12,000 years
ago than it is today.

On Fri, 13 Jul 2012 15:55:07 -0700, Pamela Clark <>

The relative disappearance of Crossbills from the area could potentially be
due to climate change. Check out this recent article in Science News about
how the warming climate means shifting ranges and mixed-up relationships
for a lot of species.


Joseph Morlan, Pacifica, CA
"It turns out we're very good at not seeing things" - Jack Hitt

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