Date: 5/16/19 6:31 am
From: Mike Patterson <celata...>
Subject: [obol] Re: Malheur empids
I attach the relevant portion of the NAB account below, which roughly
translates to: don't fool yourself. It's probably not possible to
sort Western Flycatchers in zones of overlap (Eastern Oregon) no matter
how nuanced you believe your hearing is...

From: Lowther, P. E., P. Pyle, and M. A. Patten (2016). Pacific-slope
Flycatcher (Empidonax difficilis), version 3.0. In The Birds of North
America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca,

"Species limits in the E. difficilis complex, which includes both E.
difficilis sensu stricto (the Pacific-slope Flycatcher) and E.
occidentalis (the Cordillean Flycatcher), are controversial. Despite his
extensive, detailed data set and analyses, Johnson 1980b concluded that
the only clear species break was between E. difficilis sensu lato and E.
flavescens, although he revised this view after allozyme data were
available (Johnson and Marten 1988) and then moved to have the species
split, a proposal accepted by the American Ornithologists’ Union
Checklist Committee (American Ornithologists' Union 1989). Evidence for
the split rested on apparent genetic and vocal divergence, yet Phillips
1994c and Pyle 2012 noted that plumage and mensural characters allowed
for only a statistical, not a biological, distinction; moreover,
evidence for assortative mating is weak, with a mere two pairs
documented (Johnson 1994c). Conversely, a mixed population breeds in
northeastern California (Johnson 1980b, Johnson 1994c), where
“bilingual” birds have been recorded, although even in allopatry songs
and calls differ only in certain details (Johnson 1980b)—i.e., they are
more similar than different (see Sounds: Vocalizations). Ostensible E.
occidentalis at the eastern base of the Cascades in Washington utter
Position Notes of E. difficilis sensu stricto (Tweit et al. 1990, Smith
et al. 1997), and birds with E. difficilis Position Notes of have been
found inland as far east as Missoula, Montana (C. A. Marantz, personal
communication). A comprehensive genetic analysis of breeders in the
Rocky Mountains of southwestern Canada found hybridization and
introgression between the species (Rush et al. 2009c). The existence of
hybridization between Pacific-slope and Cordilleran flycatchers raises
concern about the decision to split these species; however, the authors
also reported that "allopatric populations are genetically distinct in
both mitochondrial and nuclear DNA, and the hybridization might not
affect populations outside of the contact zone" (Rush et al. 2009c)."

Mike Patterson
Astoria, OR
Bald Eagles - a gateway bird
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