Rob wrote:

> >a couple of weeks ago, I heard the leader to a piece on NPR, the gist of
> >which was that birds are good indicators of global warming; i.e., as the
> >climate warms, birds will find suitable habitat in more northerly areas
> >that would previously have been inhospitable. This may help explain the
> >northward range expansion of scrub jays and grackles, for instance, and
> >maybe such oddities as little blue herons in the Bay Area, or summer
> >tanagers in Sacramento. I didn't, unfortunately, hear the whole piece,
> >which typically would have included someone with an opposing or alternate
> >viewpoint. Anyone have any critiques of this theory? Know of any published
> >references on this topic? Thanks...

then Don answered -

> I know there's been some published work on the average departure
> and arrival time of raptors in eastern Canada over the past
> two ?I think? decades. I've not read the paper(s) myself, have just
> seen references...
>
> The gist of it is that they've been arriving and nesting earlier,
> and it's statistically significant (obviously, there's annual
> variation which must be taken into consideration).
>
> Such correlations might be related to global warming, might be
> due to other causes, but as more and more of them are discovered
> and as work is done which ties down causes when possible, I'd
> be very, very surprised if the case for global warming were in
> any way weakened...

Check out any of the *.meterology.* usenet lists and you will see that there
is lots of debate about global warming. Not whether it is occurring or not -
that is irrefutable - but whether it is anthropogenically forced or otherwise.
The problem we humans have is that our observational period of record is
measured in a couple of hundred years which is the blink of an eye in
geophysical terms, thus our comparative analyses lack good data.

As for birds taking advantage of global warming, I think there is plenty of
evidence for the fact that birds will colonize any habitat that suits them.
Lazuli Buntings and Willow Flycatchers have been pressing northward steadily
through BC the past decade. The population to the south is far from saturated so
I doubt that it is due to territorial expansion pressures.





==========================
Jack Bowling
Prince George, BC
jbowling at direct.ca