Wayne W. wrote -


(big snip)
<<< I hasten to add that my experience that 2 species of brown thrush
do not usually breed in the same forest stand does not always hold in
other parts of North America, where different habitat types occur, and
other species of thrush (Gray-cheeked Thrush, Bicknell's Thrush, and
Wood Thrush) are added to the equation. The range of habitat types
used by a species depends on the range of habitats available, as well
as on the presence of other potentially competing species.>>>

There are 3 species of catharid thrushes in the northern half of BC -
Swainson's, Hermit and Gray-cheeked. Hermits like young/scrub
conifer/deciduous type habitats; Gray-cheeked like mostly
moister willow/alder scrub apparenty; and Swainson's more mature
deciduous/confier mix. I have almost zero experience with Gray-cheeked.
In my experience, there is little overlap in breeding habitat selection
between Hermits and Swainson's: one would not expect to find Swainson's
in pine flats, nor would one expect to find Hermits in big tree forests.

(snip)

<<< One of the things that I find intriguing about the
Veery/Swainson's Thrush/Hermit Thrush situation is that there is, in
general, an altitudinal succession of species, with Veeries at the
lowest altitudes, Swainson's in the middle altitudes, and Hermits at
the higher altitudes, although there is a lot of overlap.>>>

With latitudinal compression of biotic zones, this altitudinal
zonation disappears north of about Quesnel or 53 degrees north in BC.

<<< A similar situation, where you get an altitudinal succession of 3
closely-related species (over a narrower range of altitudes) was found
by Robert Weeden, who studied ptarmigan (Willow, Rock, and
White-tailed) in the Chilkat Pass area of extreme northwestern B.C. He
found that Willow Ptarmigan nested at the lowest altitudes, in the
dense willow thickets above the limit of conifers; that Rock Ptarmigan
occurred higher up, in alpine vegetation above the willow thickets;
and that White-tailed occurred highest, where the landscape was
dominated by rocks and scree rather than vegetation. Once again, the
picture changes in areas where one of the 3 species drops out, such as
the northern Rockies of B.C. (where there are White-tailed and Willow
but no Rock Ptarmigan), or in the Coast Range between the Skeena River
and Vancouver (where there are Rock and White-tailed Ptarmigan but no
Willows).>>>

Bzzztt. Rock Ptarmigans indeed do occur in the Northern Rockies, e.g.,
the female myself, Chris Siddle, Gary Davidson and Linda van Damme
witnessed near the Summit Lake radio tower in Stone Mt. P.P. July 1,
1986 (willow thickets at this elevation, too). The species has also
been reported from Pink Mt. Anyone making bold statements about
ptarmigan distribution in BC will be talking mainly through their hat
since there has been very little work done on alpine avian species
anywhere in the province.

<<< When I say that two species of "brown thrush" do not usually
breed in the same forest stand in our area, I'm trying to describe the
big picture, and there may be some local exceptions. Would anyone else
like to share their experience with these species?>>>

I agree with the general statement. Note that Swainson's coexist
happily with Varied Thrushes and Am. Robins so the habitat selection
seems to be catharid specific.

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