[obol] Re: Black Butte Swamp thrush question
- From: David Irons <llsdirons@xxxxxxx>
- To: STEVE KORNFELD <sbkornfeld@xxxxxxx>, OBOL Oregon Birders Online <obol@xxxxxxxxxxxxx>, "cobol@xxxxxxxxxxxxxxxxxxxxx" <cobol@xxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 3 Jun 2014 08:25:31 +0000
Steve at al.,
As Wayne Hoffman wrote earlier, sorting out Swainson's Thrushes is not too hard
given a decent view. Birds of both the Russet-backed and Olive-backed groups
occur in Oregon, with Russet-backed being the expected form from at least the
crest of the Cascades west to the Pacific Ocean. If you look at the Oregon
Breeding Bird Atlas (BBA) map for Swainson's Thrush in Birds of Oregon: A
General Reference (BOGR), you'll notice that there is a significant gap in the
distribution of breeding Swainson's in Oregon. Western Oregon (the area west of
the Cascades) is blanketed with hexagons where summering Swainson's were
recorded, with that blanket extending across the Cascades crest into the
westernmost reaches (higher wetter slopes) of the four eastside counties that
abut the Cascades (Wasco, Jefferson, Deschutes, and Klamath). Then there is a
rather spotty distribution of hexagons where breeding season Swainson's were
recorded (during the 1995-1999 surveys) until you get over into the Blue and
Wallowa Mtns, where there is a pretty solid blanket of detections.
Unfortunately, the BOGR account doesn't really address which type occurs in the
Blues and Wallowas and perhaps the Ochoco Mtns from looking at the map, but I'm
presuming that these are Olive-backed birds. I agree with Wayne's suggestion
that the birds you saw were probably of the Pacific Coastal Russet-backed
group.
It is certainly worth paying close attention to Swainson's Thrushes when you
see them, particularly those found east of the Cascades crest. Olive-backed
birds were recently discovered breeding west of the Cascades crest in nw.
Washington and it may be that there are some areas along the crest of the
Oregon Cascades where both types can be found. Some of these questions have
received very little if any study aside from specimen review. With a decent
digital camera and some focused effort any of us can endeavor to answer such
questions. I just spent much of the past weekend birding in southern Morrow
County, which extends into the westernmost section of the Blue Mountains. We
saw and heard no Swainson's Thrushes, despite being in habitats that seemed
reasonably suitable for this species. More surprisingly, we saw and heard no
Hermit Thrushes either. Our only Catharus thrush of the weekend was a Veery
that we found right in the town of Lexington. On Friday, Jim Danzenbaker, who
was traveling with us, saw an Olive-backed Swainson's Thrush at Deschutes River
State Park in Sherman County. I tried to relocate the bird, but never saw it.
As for White-breasted Nuthatches, birds found in the Willamette, Umpqua, and
Rogue Valleys are generally assigned to the subspecies aculeata. Steve
Mlodinow, who is currently working on an article about the identification and
distribution of western White-breasted Nuthatches told me recently that the
birds in extreme western Klamath County (where there are some oaks) are also
aculeata. Birds that I photographed last year at Running Y Ranch do appear to
best fit aculeata. Generally, birds found east of the Cascades have been
assigned to the subspecies tenuissima, but if aculeata is found east of the
Cascades in Klamath it may not be safe to presume that birds in western
Deschutes Co. are tenuissima. I photographed a White-breasted in southern
Morrow Co. over the weekend and I am anxious to take a closer look at those
photos to see if that bird can be assigned to subspecies.
The Cascades are an intriguing zone of contact for many species and subspecies
pairs whose ranges tend to be defined by a wet slope-dry slope division. The
obvious poster children in this regard are the Hermit Warbler/Townsend's
Warbler and Red-naped Sapsucker/Red-naped Sapsucker pairs. We tend to pay
closer attention when full species are involved, but some of the subspecies
pairs are equally intriguing. There seems to be an imminent split of the
White-breasted Nuthatches on the horizon and I've heard some lesser rumblings
about splitting the Olive-backed and Russet-backed Swainson's Thrushes into two
species. Sorting the nuthatches takes a practiced eye, but separating the two
Swainson's Thrush groups is not particularly challenging.
If you look at the BirdFellow ID gallery at the link below, the first two
images were
both taken in Oregon. The first, is a Olive-backed migrant that I
photographed at Malheur HQ during Memorial Day Weekend a couple years
ago. The second is a Russet-backed bird that I photographed at Grand
Island, Yamhill County.
http://www.birdfellow.com/birds/swainsons-thrush-catharus-ustulatus#/idPhotos
Dave Irons
Portland, OR
From: sbkornfeld@xxxxxxx
To: obol@xxxxxxxxxxxxx; cobol@xxxxxxxxxxxxxxxxxxxxx
Subject: [obol] Black Butte Swamp thrush question
Date: Mon, 2 Jun 2014 18:11:14 -0700
Greetings.
Birded the Black Butte swamp this am coming in from the Glaze Meadow side.
Very active with abundant vireos, flycatchers, warblers and woodpeckers. My
hope was Veery with previous reports from years past. No luck with Veery.
Swainson's Thrush were scattered in the swamp. Hoping to sort out Interior
West versus Pacific. Are these Swainson's spill overs from the other side of
the Cascades or part of the interior west population? Similar question to
White-breasted Nuthatch and a few others.
thanks
Steve Kornfeld
Bend
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