[obol] Re: dowitcher picture, help with ID
- From: David Irons <llsdirons@xxxxxxx>
- To: DJ Lauten and KACastelein <deweysage@xxxxxxxxxxxx>, OBOL Oregon Birders Online <obol@xxxxxxxxxxxxx>
- Date: Mon, 13 May 2013 05:52:51 +0000
Greetings all,
Just got home after being out of town and away from my computer all weekend. I
see that a couple of others have weighed in on these birds already. I by
offering that I believe all three birds in Brandon's photos are Long-billed
Dowitchers. However, before deciding which species you have, I think that there
are a couple of important steps to follow. One relates to shorebird ID in
general and the second is dowitcher specific.
Step 1: With any shorebird, the first question is age/plumage.
The orange/cinnamon underparts of these dowitchers makes them adults in
alternate ("breeding") plumage.
Step 2: If you think you are looking at an alternate-plumaged Short-billed
Dowitcher, geography is a factor in the appearance of the bird. You need to
know which of the three subspecies is expected where. In Oregon, the expected
subspecies is L. g. caurinus, referred to by Sibley and others as the "Pacific"
form. The nominate subspecies L. g. griseus–generally referred to as the
"Atlantic" form–breeds in eastern Canada and migrates along the East Coast of
North America. To my knowledge this subspecies has never been documented in
Oregon (it would be very tough given the similarity to caurinus). A third
subspecies, L. g. hendersoni, is generally called the "prairie" or "interior"
form, as it breeds in central Canada and migrates mostly through the center of
the continent, with few detections on either coast. A quick look at Brandon's
photos readily takes two of the three Short-billed Dowitcher subspecies out of
consideration. Alternate-plumaged griseus and caurinus show extensive white on
the belly, with the bright cinnamon/orange limited to the throat, foreneck and
upper breast. Further, they have heavy dark barring from just below the
shoulder down the length of the flanks. None of the birds photographed by
Brandon have white bellies, nor do they show extensive enough cinnamon/orange
below or enough dark barring on the flanks to be either griseus or caurinus.
Having gone through the fairly straightforward process above, we can reduce the
potential identifications of these birds from four taxa (Long-billed Dowitcher
and three subspecies of Short-billed Dowitcher) down to two (Long-billed
Dowitcher and one subspecies of Short-billed Dowitcher). Given that the
underparts are almost completely orange/cinnamon, these birds all have to be
either adult alternate-plumaged Long-billeds (only one subspecies) or adult
alternate Short-billeds of the L. g. hendersoni subspecies. At this point it
should be noted that at best hendersoni Short-billed Dowitchers should be
considered rare but annual migrants in Oregon, Washington, and California and
that the well-documented detections of this form along the Pacific Coast are
few and far between. As a general rule, it is relatively safe to assume that if
you see an alternate-plumaged adult dowitcher in Oregon (particularly western
Oregon) that is almost entirely cinnamon/orange below, it's a Long-billed.
Not being one to dismiss the possibility of hendersoni Short-billed out of
hand, I think it's important to visit the differences between Long-billed and
the prairie form of Short-billed. There are two key things to look at.
I learned about the first one from a wonderful blog piece that Greg Gillson did
on this topic a few years back. Using photos of a bird that was originally
thought to be a hendersoni, Greg pointed out one critical field mark that we
can see on all of the birds in Brandon's photos. It relates to the dark barring
on the flanks. In fresh alternate plumage (acquired during a
late-winter/early-spring molt), the dark bars seen on the flanks of Long-billed
Dowitchers are subterminal dark bars on the feathers, with the tips of those
feathers and most of the others on the flanks and belly being fringed with
white (wears off quickly later in the season). With hendersoni Short-billed
Dowitchers, the dark barring is terminal (on the tip of the flank feathers) and
there is no white fringing on the underparts. Looking closely at Brandon's
photos, all three birds show white fringing on the belly and flank feathers,
including those with subterminal dark barring. Here's a link to Greg's
excellent ID
piece:http://thebirdguide.com/identification/dowitchers/interesting_dowitcher.htm
Another good field mark in separating this pair is the presence or absence of
spotting on the foreneck and throat. Long-billeds have spotting on the foreneck
and throat, while hendersoni Short-billed Dowitchers are almost entirely
lacking in spotting on the foreneck and throat.
Whenever anyone asks me about dowitcher ID, I invariably point them to the
Sibley Guide, which for my money offers the best treatment of Short-billed and
Long-billed Dowitchers of any of the standard (non-specialty/family group)
guides. I really like the accuracy of his illustrations and if you look closely
at his paintings of Long-billed Dowitcher and hendersoni Short-billed
Dowitcher, the field marks described above are all shown. Though it is not
mentioned in Sibley's arrowed text, his illustration of Long-billed Dowitcher
the white fringing on the flanks of the alternate-plumaged adult.
As chance would have it, Shawneen Finnegan and I encountered a couple of flocks
of alternate-plumaged adult Long-billed Dowitchers near Tillamook today. I took
a few photos, one of which shows the field marks discussed above. It can be
viewed at the link below:
http://www.birdfellow.com/members/dave_irons/field_reports/782-long-billed-dowitchers-along-the-wilson-river-12-may-2013
Dave IronsPortland, OR
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