> >From Michael Hobbs:
> I don't know about studies, but I do know that on the East coast,
> several prominent species have moved northward over the last 30 years.
> These include Northern Cardinal, Northern Mockingbird, and Tufted
> Titmouse.

To which you can add Red-bellied Woodpecker (as Scott Richardson would
point out, another bird that depends on feeders in the winter in the
new northern part of its range).

In fact, all the dramatic range changes that come to mind in East Coast
birds, no matter whether northward, southward, or outward, seem to share
human intervention as causes. Herring and Great Black-backed Gulls have
exploded southward during the same time frame (well, after the Cardinal's
northward push, but parallel to the other three). The Double-crested
Cormorant exploded south and inland. Various Herons and Egrets continue
their nearly century long expansion north, and House Finches, of course,
have been exploding in every direction (well, except east into the open
ocean) since their 1940s release on Long Island, NY. In all these cases,
human intervention seems to be the best explanation: food at dumps for the
gulls, removal of persecution for the herons, egrets, and cormorants, and
introduction to a new range of abundant suburban habitat for the finches.

There may be more subtle changes in ranges that are more climate mediated,
but the really noticable ones don't seem to have climate as a major
factor.

Chris Hill
Everett, WA
cehill at u.washington.edu