Tweets,



The weird warbler we reported last Sunday at Duvall was most likely a
MacGillivray?s Warbler x Common Yellowthroat hybrid. Steve Mlodinow reports
that this hybrid has been described previously and that some had the white
throat we observed. Dennis Paulson thinks it could have been that the female
was MacGillivrays, the male the Yellowthroat, which might help account for
the otherwise puzzling white throat. The song (which I was not able to
record) could conceivably have been described as intermediate between the
songs of these two species, though if it learned its song from nearby
songsters it?s a puzzle what species those might have been. If anyone is in
the area and would like to try to relocate it, the GPS coordinates are N
47.73347, W 121.98959.



Hal Opperman sent me a copy of a recent publication on the genetic evidence
for hybridization between Pacific-slope and Cordilleran Flycatchers across
southern BC and sw Alberta (which would apply as well to our northern tier
of counties. (Andrew C. Rush, Richard J. Cannings and Darren E. Irwin.
?Analysis of multilocus DNA reveals hybridization in a contact zone between
Empidonax flycatchers,? J. Avian Biol. 40: 614-624, 2009.) Much of the
article was devoted to technical methodological accounts of the laboratory
procedures for comparing DNA, both mitochondrial and nuclear, which I take
on faith.



The results were instructive and support my view of the issue by-and-large.
Compared with California reference samples for Pacific-slope Flycatchers and
Cordilleran reference samples from Arizona, Colorado and South Dakota,
Canadian samples from the Cascades and west were essentially Pacific-slope,
but individuals from east of the Okanagan River valley to the Rocky
Mountains of southeastern BC and southwestern Alberta were intermediate in
nuclear DNA comparisons but close to Pacific-slope in their mitochondrial
DNA (which, unlike nuclear DNA, is transmitted without genetic recombination
through the maternal line). Genetic patterns varied clinally from west to
east. They were cautious in their conclusions vis-?-vis the validity of the
split but indicated that the two population may have been isolated for
350,000 years before contact was reestablish in this zone.



This pattern is quite comparable to what has been found with respect to the
hybridization of Hermit and Townsend?s Warblers and is perhaps similar as
well to our vexed ?Northwestern Crow? issue as well as the ?Olympic Gull.?
In all these cases there is a broad zone of clinal variation between
putatively ?pure? parental populations of two ?species.?



Not reported here but described by Cannings and myself in a 1993 manuscript,
the song features also vary clinally west to east from Okanogan County to
Pend Oreille County, and on southward to the Palouse and Blue Mountains,
where the populations are ?by decree? Cordilleran.



So, the breeding Western Flycatchers in Ferry, Stevens, Pend Oreille, and
northern Spokane counties should probably be simply listed as ?Western
Flycatchers.? Sorry if that messes up your county lists.



Gene Hunn

Lake Forest Park, WA

enhunn323 at comcast.net