[reccom] Pacific-slope Flycatchers

[Mark Stackhouse]

I've spent some time reviewing the situation in the Southwest regarding 
"Western" Flycatchers in migration, and have received some excellent 
input from members of both the Arizona and Nevada records committees 
regarding the occurrence of these in their states.

There are, and remain, serious issues with this split - the genetics 
are not that clear, and there probably hasn't been enough analysis in 
the contact zone, which is now known to be much larger than previously 
thought. The two "species" come into contact over a large area of 
British Colombia/Alberta, where intermediate individuals (at least in 
terms of vocalizations) are reported frequently. The best case for a 
split in this complex may be for the Channel Islands birds of 
California, that are currently considered a subspecies of 
Pacific-slope. Much more work needs to be done.

That being said, the AOU currently recognizes the split as we all know 
it, and inasmuch as we follow the official AOU checklist, we need to 
decide what to do about this in Utah.

Neither Arizona nor Nevada have any hard evidence to back up the 
conventional wisdom regarding the migrational occurrence of 
Pacific-slope/Cordilleran Flycatchers in their states. Neither species 
is a review species in either state - they are both assumed to occur. 
The closest to any non-circular reasoning evidence regarding these is 
from Martin Meyers (NV committee secretary), who said:

"I expect that, if we were to ever be able to reliably identify these 
critters, we'd find that the overwhelming number of birds in the 
traditional low-elevation migrant traps are PSFL.  In spring, many of 
the birds call.  In all of the birding Greg Scyphers and I have done, 
neither of us has ever heard a "typical" COFL call at any of these 
locations.  We have heard many "typical" PSFL calls.  Understanding 
that COFL (as, for example, from the Warner Mountains in NE California) 
regularly give a PSFL-type call, one would still think, just based on 
the odds, that if there were numbers of COFL coming through, at least 
ONE would have given a typical COFL call.  But that's hardly "hard 
evidence"."

In reality, COFL gives PSFL "male position notes" (the familiar call) 
much more often, and over a wider range, than previously thought. 
Here's what Gary Rosenberg of the AZ records committee had to say:

"Your assessment of the status of Pac Slope and Cordilleran Flycatchers 
is spot on! I believe that there may actually be specimen evidence for 
Pac Slope in AZ (maybe in winter), but virtually all of the records are 
either based on calling birds - and I agree 100% that the calls are 
almost certainly nonreliable/overlapping, and worse, probably only 
reliably reported by a handful of observers - meaning most observers 
would have a difficult time differentiating the subtlties between the 
two call types. Also, most of the published reports of Pac Slopes are 
basically based upon being found in the lowlands during migration - the 
conventional wisdom is that Cordilleran does not pass through the 
lowlands, but "arrives" on the breeding grounds in the mountains 
directly! This of course is a product of circular reasoning - this may 
indeed be the case, but the idea is based upon observers "believing" 
this and thus identifying all lowland birds (silent that is) as Pac 
Slopes - or "Westerns"."

And further info from AZ from Mark Stevenson on the actual evidence 
they have:

"Monson and Phillips 1981 "Annotated Checklist of Birds of AZ" lists 4 
subspecies of  "Western Flycatcher" as having been found in AZ, 
presumably based on specimen evidence since it was Phillips. They say 
E. dificilis hellmayrii (Cordilleran) is scarce as a transient and that 
E d dificillis far outnumbers E d h as a transient. They noted E d d 
(Pac-slope) being --->>>found only twice in N AZ<<<--- (both in fall, 
near Flagstaff). In Birds of AZ 1964 they said the same thing, that as 
a migrant E d h is far outnumbered by E d d but don't go beyond that. 
Again, this is presumably based on specimen evidence as that was the 
only evidence that Phillips valued. Whether the criteria that Phillips 
used for determining subspecies would be accepted by today's 
systematists/banders is unknown to me. He didn't seem to express the 
caveats that Pyle does in discussing the separation of hellmayrii from 
dificilis. I'm not aware of any DNA analysis of "Western" in AZ, but 
that doesn't exclude the possibility. Since both are known to be common 
here in their place/time, there's less motivation to "prove" what any 
particular "Western" is.

If I were in Mark Stackhouse's shoes, I'd be very cautious / skeptical 
too of calling a winter "Western" to species."

So there we have it. I don't know if this gives us any help, but we 
have a decision to make, and I'm sure that Rick is correct in his 
analysis regarding lowland migrants and winter birds. We could "punt" - 
that is do the same thing as our neighbors, assume that these actually 
do separate out by habitat/season, and acknowledge the circular 
reasoning involved, waiting until the AOU sorts out the larger issues. 
We could stay "pure," and reject any occurrence of PSFL in Utah until 
we're able to get definitive evidence in terms of DNA or in-hand 
specimens and calls. Or we could do something in between, and accept 
only PSFL records that come with vocalizations and are consistent with 
the "conventional wisdom" of habitat and season.

Only if we decide on the "punt" option do we accept the current record 
under review. I really don't have an answer, but put this forth for 
discussion, and look forward to the opinions of the rest of you.

Isn't this fun?!?!?

Mark Stackhouse
Westwings, Inc.
www.westwings.com
mark at westwings.com
801-487-9453 (Salt Lake City, Utah, USA)
011-52-323-285-1243 (San Blas, Nayarit, Mexico)