Michael Hobbs wrote:

>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.
>
>However, as Mr. Guttman implies, we need a study which looks at many
>species, to see if these three represent a trend, or if they are just
>part of the normal shifting of ranges.
>
>It would also be interesting to see if the southern extent of the ranges
>is also moving north.

The first and third of the species you named have probably extended their
ranges to the north because of bird feeders. Mockingbirds feed on fruit
during the winter, and there may be a lot more fruit trees planted in the
cities now. I think a lot of the obvious range extensions of birds--in any
direction--in recent years have been responses to changes in habitats (or
food resources) brought about by humans.

There are very interesting articles in the Cooper Ornithological Society
symposium, "A century of avifaunal change in western North America," J. R.
Jehl, Jr., and N. K. Johnson, eds., Studies in Avian Biology No.15, 1994.

Dennis Paulson, Director phone 206-756-3798
Slater Museum of Natural History fax 206-756-3352
University of Puget Sound e-mail dpaulson at ups.edu
Tacoma, WA 98416