Dear Michael Hobbs and Tweeters:

Which is more common, Swainson's or Hermit Thrush? Depends where
you are! In the Vancouver, B.C. area (where I have done some
quantitative surveys), Swainson's is one of the most abundant breeding
birds, in both broad-leaved and coniferous forest, from sea level up
to about 3000 feet altitude. There is a narrow belt from about 2700 to
3300 feet (e.g., on Mount Seymour) in which both species breed. Above
that, Hermit Thrush becomes one of the most abundant birds, and
Swainson's drops out. The lower limit for Hermit Thrush generally
coincides with the point at which openings (resulting from heavy
winter snowpack) appear in the forest. Hermits generally shun the
unbroken forest that Swainson's prefer.
In the B.C. southern interior, the picture is complicated by
Veeries, which generally exclude Swainson's from cottonwoods and other
riparian vegetation below about 2500 feet. The zone of overlap between
Swainson's and Hermits is higher (about 4500 to 5000 feet) and
possibly broader, but Hermits again dominate in the more open forest
stands from about 5000 feet to timberline (at 7000 to 7500 feet).
Which is more abundant overall? Probably Swainson's, because its
habitat occupies a much larger area than the Hermit Thrush's. Breeding
bird surveys and other data suggest that Swainson's Thrush is one of
the 5 most common breeding birds in the entire province of B.C.
Hermit Thrush, although common enough, probably wouldn't make the top
ten.

-----Original Message-----
From: Michael Hobbs <Hummer at isomedia.com>
To: Marguerite Bevis <mfly.bevis at worldnet.att.net>;
tweeters at u.washington.edu <tweeters at u.washington.edu>
Date: Tuesday, June 15, 1999 9:39 PM
Subject: Re: Swainson's Thrush


>> So, which are more common, the Hermit or Swainson's Thrush?
>
>Hermit Thrush pass through the Puget lowlands in largish numbers
during the
>last 3 weeks of April, heading north and up. They are mostly silent
during
>migration (at least, they don't usually sing), so many pass
unobserved. They
>breed at higher elevations (above 1000'?). They dribble back down
during
>September and October. They are present in the Seattle area all
winter long,
>but in quite small numbers.
>
>Swainson's Thrush begin arriving in early May, and by June they are
one of the
>most numerous nesting birds. At this time of year, they are
plentiful and
>noisy, giving both their "WhiDDTT" call and their rising spiral flute
song.
>They are, however, somewhat difficult to see. As often as not, they
will sing
>from the interior branches of a tree. Looking for them on an exposed
perch is
>often futile. They tend to be lower down than you might think, and I
often see
>them on or near the ground. When they notice you, they often freeze
for a
>moment, as if deciding whether to flee. Then they vanish.
>
>== Michael Hobbs
>== Kirkland WA
>== hummer at isomedia.com
>