I'll just add my two cents to this topic. Mike Patterson's message
about this was right on the money. There are so many more birds
migrating through the East than the West that there's just no way we
can equal their numbers. Most of the passerine migrants we get here
come from BC and southern/western Alaska, while New York is getting
them - literally - from a huge area to the north and west of it. The
East gets migrant passerines from all across the boreal forest, west to
at least central Alaska (!), This is thought to be because as the
glaciers receded, the eastern birds spread farther and farther west
into the boreal forest but still retained their ancestral migration
patterns. That forest is a fantastically rich producer of songbirds,
and that's why there is a lot of concern right now about the rate of
logging all across the boreal forests of Canada. In addition, as Mike
said, there are so many more species in that area. You can have 20-25
warbler species in a day of migration in the East, while we would be
thrilled to see 5 warbler species in a migration fall-out. We have a
rich avifauna in the West, but remember we are very far north, so a lot
of our diverse collection of breeding species just pulls out in the
fall without much fanfare. Just think if we had big fall-outs of
Western Tanagers (I've seen this several times), Bullock's Orioles,
Lazuli Buntings, and Black-headed Grosbeaks. These and other species
just arrive in spring and set up territories, in part because we're at
or near the northern extent of their ranges, and then they just leave
in fall.

Of course the eastern fall-outs aren't at all what they used to be, as
bird habitat disappears in all parts of their ranges, and the wintering
grounds of eastern birds may have been more depleted than those of our
western birds. It's not by any means certain whether changes on
wintering grounds or breeding grounds are the most significant in
population declines of migrant birds, but it's certain that both of
them play their parts. It may be that loss of habitat on the migration
pathway is similarly important.

We sometimes get fall-outs in the Pacific Northwest, but in my
experience, they are dominated by one or a few species (I've
occasionally seen Yellow-rumped and/or Wilson's Warblers and/or
Warbling Vireos in huge numbers), with very small numbers of a few
additional species. It's nothing like an eastern migration (darn it).

Dennis
-----
Dennis Paulson
1724 NE 98 St.
Seattle, WA 98115
206-528-1382
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