On Tue, 7 Jul 1998 mpdossett at juno.com wrote:
> I saw 5 Nashville Warblers less than a fourth of a mile up the Cedar
> Creek trail 18 miles west of Winthrop on Saturday. Although this spot is
> only about 3,500 feet, I was still somewhat surprised because it did not
> seem like the type of habitat they might prefer. There were several
> Ponderosa pines as well as other types (Lodgepole? I don't know many
> conifers yet) There were also Doug Firs, Western Cedars, and some Hemlock
> (definately not the brushy hillsides Andy S. was talking about). This
> surprised me and kind of took me off guard because I always thought of
> Nashville Warblers being more typical of the western slopes of the North
> Cascades (such as between Newhalem and Diablo lake), rather than the
> eastern. The Checklist for Birds of the North Cascades National Park,
> including the Ross Lake National Recreation Area and the Lake Chelan
> National Recreation area lists Nashville Warblers as being "Uncommon.
> Widespread in very small numbers or common only within restricted
> habitat" So do Nashville Warblers show a preference for which slope
> based on habitat?

Nashvilles are most typical of moderatley dry (but not too dry) forest
zones of the east slope of the Cascades. They are near the edge of their
breeding range in the Ross Lake/Diablo Lake area.

In the northern Cascades, the geographic crest runs along the
Whatcom/Okanogan County line. However, the ecological east/west division
is closer to the vicinity of Ross Lake. So Nashvilles around Ross Lake
are really in east-side-like forest zones. In the southern Cascades, the
geologic crest (and the ecological division) runs mostly through Skamania
County, but as the latitute is decreasing, forests are getting warmer, and
Nashvilles can breed (at least locally) west of the crest in Skamania,
Clark, and possibly even Lewis County. (It is a little surprising that
they don't breed in locally warm, low-lying areas of the Sound, since
many typically east-side species that breed in Clark County can also breed
in low-elevation, rain-shadowed west-side habitats.)

I think what I'm trying to say (and I'm not sure I'm answering the
original question!) is that west-slope birds are mainly occupying the more
east-slope type environments on the west slope. Possibly they do pick
somewhat different habitats on the west slope, since they might be trying
to compensate for the wetter conditions by choosing the driest
microhabitats on the west side.

Kelly Cassidy
Seattle