Date: 5/16/19 6:27 am
From: <clearwater...>
Subject: [obol] Confusing "Western" Flycatchers in eastern/central Oregon
Interesting discussion. It's important to keep in mind that the research leading to the AOU's split between Pacific-slope and Cordilleran Flycatchers relied on genetic work and in-hand measurements, not just (or even primarily) on vocalizations. With that in mind, it seems wise to avoid use of the term "intergrade" or "hybrid" to describe male birds whose songs or male position notes (MPNs) are somewhere on the cline between "standard" examples of Cordilleran and Pacific-slope.

I just went back to re-read Arch McCallum's remarks on this species pair.

[ http://www.appliedbioacoustics.com/Repertoires/Passeriformes/Tyrannidae/Empidonaxdifficilis/index.html | http://www.appliedbioacoustics.com/Repertoires/Passeriformes/Tyrannidae/Empidonaxdifficilis/index.html ]

Arch was cautious in his statements regarding the implications of the observed variations in vocalizations, though he did suggest that his sample from the Warner Mountains *might* be indicative of gene flow between these species.

The idea that some "Western" Flycatchers in the Warner Mountains give different MPNs at different times of the day may stem in part from a bird that I reported at Willow Creek Campground in 2003. When Arch visited that site ("Warner Territory 10" in his labeling of field sites), he found a bird that, depending on time of day, sometimes gave just the second phrase of its song, in the manner of a MPN. That might explain the difference that I noticed. The explanation of such birds as "bilingual" may be oversimplified.

The north slope of the Ochoco Mountains (southern Wheeler County) is another place where there seems to be some confusing overlap in types of vocalizations. In one spot near Courthouse Rock where spray from a small waterfall creates a lush, moist oasis, I've consistently found birds that give Pacific-slope-type MPNs indistinguishable from the birds here in the Willamette Valley. Farther east along the Barnhouse BBS route, I once found a bird that gave very distinct Cordilleran-type MPNs, but in other years I've heard birds that sounded more like Pac-slopes.

To me, the blanket term "Western Flycatcher" makes a lot of sense for birds detected in Oregon anywhere east of the Cascades crest, at least until you get to the Blue Mountains and Wallowas. You can't tell them apart visually, and it's not clear that vocal differences are reliable for sorting out birds in this area.

This might be a little frustrating for birders who are concerned with how to "score" individual flycatchers on their state or county lists. But birder frustration isn't a criterion for lumping vs. splitting species.

It's not these birds' problem if we can't sort them out in the field. Apparently they seem to figure it out most of the time, though -- as with members of the Yellow-bellied/Red-naped/Red-breasted Sapsucker species complex -- it's not a 100% thing.

Tsee'eep,
Joel

--
Joel Geier
Camp Adair area, Pacific-slope territory

 
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