Date: 1/9/18 11:49 am
From: Jay Withgott <withgott...>
Subject: [obol] "Yellow-shafted Flickers" in Oregon -- a plea for closer observation

Craig Tumer raises a great point about the putative Yellow-shafted Flicker visiting Casey's feeder, and I agree with him. As an eBird reviewer for Multnomah Co., I've wrestled with descriptions and photos of this bird and of many other flickers for a while now. Although there may be multiple birds involved, I suspect, from the timing of various reports, that the bird in Steve Jaggers' photo is the same individual seen and photographed by others in recent days (e.g., nicely by Audrey Addison here: ebird.org/ebird/view/checklist/S41505947). These photos indeed show a bird with mostly Yellow-shafted characters, but also with grayish auriculars and throat.

Much comes down to what we want to call "pure" versus what we want to call an "intergrade" -- i.e. how pure does a flicker have to be to be "counted" as a pure bird? Should a bird that looks 90% like a Yellow-shafted Flicker be counted as a Yellow-shafted Flicker? What about a bird that looks 95% like one? How about 75%?

Red-shafted and Yellow-shafted Flickers breed together in an intergrade zone across a long swath of Alaska, BC, and the Rockies, producing vast numbers of intergrade offspring that migrate southward and outward into Oregon and many other states in the winter. These offspring show a wide variety of appearances and include just about every possible combination of field marks. And then there are the backcrosses. When an intergrade bird breeds with a pure bird, they produce a batch of offspring that are genetically 75%/25% and morphologically all over the map. And then there are the backcrosses breeding with backcrosses -- etc., etc. Over time, it all makes for a complex swarm of birds ranging in their "intergradedness" from 0% to 100%.

In 2014, Oregon's own Steve Shunk tackled the flicker issue by authoring an article in Birding magazine (see link at bottom). Steve listed 6 characters we should look for in the field -- any one of which could reveal introgression (genetic mixing of populations) and disqualify a bird from being purely Yellow-shafted or Red-shafted:
* malar stripe
* feather shaft color
* nape patch
* throat color
* ear patch
* crown color
I'd urge everyone to read this article for the details. Other resources and photos are available online and make some of the same points. The bottom line is that any given individual flicker cannot safely be identified as a "pure" bird without seeing all six of these field marks clearly. That means that, if one adopts this standard, seeing bright yellow underwings and undertail is NOT in itself good enough for an identification of "Yellow-shafted Flicker".

So.... if one feels that any bird showing any discernable evidence of introgression should be considered an "intergrade"-- even one that checks 5 out of the 6 boxes above -- then a great many of Oregon's reports of "Yellow-shafted Flicker" are likely intergrades, including the bird at Casey's feeder.

I personally feel that there's no right or wrong answer as to where we "should" draw the line between "pure" and "intergrade", but I guess I also feel that the most rationally objective way to approach the question is to apply the strict interpretation adopted by Steve Shunk. This is perhaps the most biologically meaningful way to approach it, since even modest evidence of intergradation at least tells us something about whether a given wintering bird in Oregon is likely coming from the interior west or from farther east.

As an eBird reviewer, I'm going to be reassessing records in my region more critically and suggesting that our team of Oregon reviewers standardize our approach to reports of Yellow-shafted Flicker.

And for all of us as observers, here's my plea: Let's please attempt to observe all putative Yellow-shafted Flickers carefully (and photograph them, if possible), endeavoring to observe all six of the field marks noted above. Underwing color alone should NOT be considered good enough, and this is a tougher ID than most of us have traditionally given it credit for.

Happy flickering, everyone,

Jay Withgott
Portland



Steve Shunk's 2014 Birding article:

http://www.paradisebirding.com/Paradise%20Birding%20PDFs/steve%20shunk%20publications/PuzzlingFlickersIntrogression-Article.pdf

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