[obol] Birding Dowitchers

[DAVID IRONS]

Chuck,

You raise a great question.  One of the current trends in bird ID is to look 
for "structural" differences that can be used to separate species where 
plumage is not always diagnostic.  Personally, I have found many of these 
supposed structural differences to be very subjective and dependent on age, 
plumage and molt.  With dowitchers the latest crazes are that there is a 
difference in "loral angle", that Long-billeds are more hump-backed than 
Short-billeds, and that Short-billeds have longer primary extension in 
relation to the tail. I have made an extra effort to look at dowitchers this 
fall and summer and I don't feel comfortable relying on any of these 
characteristics to make positive ID's.  Primary length is probably the most 
useful of these three clues.

As usual with shorebirds, the first thing you have to do is determine the 
age of the bird.  With dowitchers in juvenile plumage the tertial pattern is 
diagnostic and can be used with utter confidence during August and early 
Sept when they are in fresh plumage.  As we move towards October juvenile 
birds will begin to molt into first basic (predominately gray) plumage that 
they will retain through the winter months.  Depending on how much of the 
juvenile plumage is retained you may or may not be able to tell them apart 
easily.

Adults are a different story.  In Spring, most of the dowitchers one is 
likely to see in Oregon are Long-billeds.  For whatever reason, Short-billed 
Dowitchers seem to overfly Oregon on their northbound journey.  This past 
Spring, I was fortunate to catch a day along the outer coast when there were 
strong onshore winds out of the NNW.  A variety of shorebird species were 
migrating low right along the beach that day.  I saw more SBDO and Red Knots 
in one day than I had seen in probably the last 20 Springs.  I can remember 
many years when I saw no northbound Short-billeds.

In Fall (actually mid-late summer for adults) there is a modest southbound 
passage of Short-billeds.  During this same period it is possible to see 
good numbers of Long-billeds as well.  In studying alternate (breeding) 
plumaged birds closely one can more often than not determine species based 
on plumage characteristics.  In Oregon we get the caurinus subspecies of 
Short-billed, which tends to show more white on the lower belly and 
undertail and tends to be more heavily barred on the flanks and lower belly 
than alternate plumaged Long-billeds.  Long-billeds are generally much more 
rusty red below.  It is important to remember that the prairie race 
(hendersoni) of Short-billed is almost entirely red below in alternate 
plumage and can easily be confused with similarly plumaged Long-billeds.  To 
my knowledge there are no certain records of hendersoni for Oregon.  Greg 
Gillson did an excellent comparison (using photos) on this issue last Spring 
when he thought he might have found a hendersoni at Fernhill Wetlands.  
Close examination proved the bird to be a Long-billed.  The most important 
thing to know about southbound alternate plumaged birds is that they have 
been through several months of feather wear and they are already beginning 
to replace their alternate plumage with the gray feathering they will carry 
during the winter months.  This can cause ambiguities that make some 
individuals all but impossible to identify with certainty, aside from 
hearing them call.  It is this ambiguity and the similarity the species show 
in basic plumage that drives some to attempt to find other ancillary field 
characteristics that might be used to separate the species.  I guess for me, 
and probably most of you, it is not a life-altering event if we can't ID 
every dowitcher we see.  Personally, I feel the authors of this article are 
grasping at straws.  Unfortunately, misidentified photos, and their use of 
distant shots and poor quality photos only adds to the confusion.

My advice would be to closely scutinize dowitchers in your local patch.  
Focus on learning what the juveniles look like first and learn how to 
separate them.  Most of the Short-billeds seen in Oregon are juveniles and 
they can be readily told from Long-billeds by the distinctive barred tertial 
pattern.  Then using field guides (which generally cover these birds well) 
start looking closely at adults.  I have done this myself and I end up 
realizing that there are definitely adult birds that I can't be positive 
about, especially during mid-late August when feather wear and molt start 
compounding the issue.

Good luck,

Dave Irons
Eugene, OR




>From: "Charles R. Gates" <cgates at empnet.com>
>To: "obol" <obol at lists.orst.edu>
>Subject: [obol] Birding Dowitchers
>Date: Sun, 24 Sep 2006 19:22:19 -0700
>
>I'm interested to hear comments about the article on Dowitcher ID in the
>newest edition of Birding Magazine.  The authors offer up several
>morphological cues that can be used to ID Dowitchers without hearing them.
>I'm just wondering if anyone has used the methods mentioned and what 
>results
>were achieved.  I need to re-read and study before being fully confident of
>the content of the article (I'm a little slow) but I used forehead shape on
>a pair of Dowitchers yesterday just to convince myself that they were
>Long-billed.  I thought one of the most important things I got out of the
>article is that photos are not necessarily the end all for bird ID.  I
>thought the photos in the article sometimes contradicted the text.  Anyone
>else see this?
>
>Chuck Gates
>Powell Butte
>
>
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