Thanks, Kevin, for this useful link. The text of your posting got mushed together so I'll give that link again here:
Vocalizations are certainly the most reliable way to distinguish between these two subspecies in the field, as the structural differences are subtle and there is some overlap in terms of size.
However, for birders in parts of Oregon where only one subspecies is resident, I think it's possible to develop an eye for "typical" individuals.
In the Willamette Valley, nearly all of the White-breasted Nuthatches that we encounter are Slender-billed (ssp. aculeata). When I encounter White-breasted Nuthatches east of the Cascades, such as in the Warner Mtns or Ochocos, I'm usually struck by how much brighter and more sturdy they look. The white areas on birds in the Willamette Valley are more of an off-white than bright white, and their bills are more delicate.
I don't think these differences are completely reliable, since the differences are subtle and there may even be some intergradation between subspecies where they come into contact (Hood River should be mentioned as another area where you have a high chance of encountering both subspecies).
But for Willamette Valley birders, if you spend enough time watching Slender-billed Nuthatches in good examples of oak habitat here, I think you'd most likely notice if you encountered a stray tenuissima, even before you heard it.
But luckily nuthatches tend to be talkative, so it would be a rare thing to have to rely on visual impression alone.
From : "rriparia@xxxxxxxxxxx" <rriparia@xxxxxxxxxxx>
* To : Karen Paulino <spindels@xxxxxxxxx>, obol@xxxxxxxxxxxxx * Date : Tue, 22 Oct 2019 19:51:28 -0700
Karen,To really answer your question you can visit a link provided in the article by Pandolfino, in Western Field Ornithologists, that discussed the vocal differences in white-breasted Nuthatches.www.westernfieldornithologists.org/W-B_Nuthatch/You can click on the MP3 links following the aculeata and tenuissima recordings. There at least two vocals provided for each. You can hear their distinct differences, which is basically speed/pace, and pitch/ tone. Kevin SpencerKlamath Falls, <ORrriparia...> from my Verizon LG Smartphone------ Original message------From: Karen PaulinoDate: Tue, Oct 22, 2019 5:34 PMTo: obol@xxxxxxxxxxxxx;Cc: Subject:[obol] Slender-billed nuthatchesIn the field, how does one differentiate a slender-billed nuthatch from a white-breasted
-- Joel Geier Camp Adair area north of Corvallis
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