Date: 7/4/17 7:23 pm
From: David Irons <LLSDIRONS...>
Subject: [obol] Reporting of "slash" category Townsend's Warblers in the Oregon Coast Range
Greetings all,


This is a bit of an esoteric topic. I am in the process of doing some eBird reviewing for Washington County and I have come across several recent (June–July) reports of warblers reported list birds as either Townsend's/Hermit or Townsend's/Black-throated Gray. These reports involve heard only (singing) birds. The songs of this threesome of species are highly variable geographically in terms of tone and pattern. Local dialects are many, particularly for Hermit and Black-throated Gray. In many cases it is hard to put a name to unseen birds. This is where is it is important to understand range and probability.


Hermit and Black-throated Gray Warblers are abundant breeders in the Oregon Coast Range. Hermit Warblers predominate at higher elevations and upslope habitats that are conifer dominant. As a general rule, Black-throated Grays tend to be found at lower elevations in habitats with a strong mix of red alder and big leaf maple interspersed with conifers. This includes streamside sites, where red alder is often the dominant tree species.


We are near the southern end of the breeding range for Townsend's Warbler, which does not regularly summer or breed in Oregon's Coast Range. Some migrants move north through the Coast Range, but after about the third week of May I would be surprised to find a Townsend's anywhere in Washington County. A June–July bird would be most surprising in the Coast Range, or in the upslope areas closer to Portland (Forest Park and the West Hills).


In my opinion, using either the Townsend's/Hermit or Townsend's/Black-throated Gray slash categories for the reporting of unidentified singing Setophaga warblers in these habitats is potentially misleading, as it suggests the possibility or likelihood that Townsend's is present in the Coast Range and surrounding ridge lines at this season. In my experience, they are not. For heard only Coast Range warblers whose songs can't be identified, I would recommend leaving them either unreported or assigning them to the Hermit/Black-throated Gray slash category. Use of any slash category that includes Townsend's is the least accurate way to report such birds. I can't in good faith validate such sightings, unless the observer supplies an audio recording that clearly suggests Townsend's Warbler.


Some sources suggest that Townsend's and Hermit songs are hard to distinguish and this may well be true in the contact (hybrid) zones where both species breed. There is a significant zone of breeding contact, which stretches along the crest of the Cascades (mostly higher elevation eastern slopes) from Deshutes County, Oregon north to Yakima County, Washington. Hybrids are fairly easy to find in this contact zone and I would expect that sorting out the vocalizations of unseen birds in this overlap zone is more of a challenge than it is elsewhere. Away from this hybrid zone and with seen birds that are apparent non-hybrids, I have never had much trouble telling Townsend's and Hermit songs apart. To my ear, Townsend's songs sound a bit slower, more slurry and generally less strident. Their songs generally lack the two hard notes at the end that I hear in most iterations of the Hermit Warbler song. Hermits tend to sing faster in crisper, slightly higher-pitched notes. They rarely sound "drunk," which is how I often characterize the pattern of Townsend's Warblers, particularly those heard singing away from breeding grounds and during migration.


I post this in hopes of nipping this reporting trend in the bud and saving us (Shawneen and me) some work. Shawneen and I like to query observers and get their feedback before invalidating sightings out of hand.


Dave Irons

Beaverton, OR

Washington County eBird Reviewer

 
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