Subject: [Tweeters] Hermit X Townsend's Warbler Hybrids in WA
Date: Sat Jul 4 15:08:27 PDT 2020
From: Alan Knue - temnurus at gmail.com

Hello All,

On a recent visit to Mt. Walker near Quilcene, I encountered several Hermit
X Townsend's Warbler hybrids, including one that looked very good for
Hermit until I got a good look at it's front and saw a faint wash of yellow
below the black throat. In fact every bird I saw well at this location was
a hybrid which prompts me to bring up what I believe to be an
underappreciated ID pitfall in WA. There are two hybrid zones in WA, one on
the eastern side of the Olympics near the border of Clallam and
Jefferson counties (where Mt. Walker is located) and the second one in a
broad swath of the Cascades south of Mt. Rainier to nearly the Columbia
River. These are well described in this paper by two prominent
ornithologists, Sievert Rohwer and Chris Wood, affiliated with the Burke
Museum:

https://sora.unm.edu/sites/default/files/journals/auk/v115n02/p0284-p0310.pdf

This paper also provides the methods they used to score the plumages of
specimens to ascertain whether they were looking at either species or a
hybrid. They discovered the hybrids are highly variable. They can look very
similar to either parent species- like a Hermit Warbler but with a faint
wash of yellow just below the black throat or like a Townsend's with a
faint wash of yellow or mostly white on the underparts. Hybrids can
have practically
every combination of characteristics in between the two species. The
hybrid types are not well illustrated in most field guides with only one
type illustrated in both the National Geographic and Sibley Guides and none
in Peterson's Guide. There is a great illustration on the cover of the
issue of the Auk where the paper referenced above appears. WA
ornithologist, Dale Herter, painted this illustration and it provides 6
examples of hybrid plumages plus both parents; it is a great reference to
familiarize yourself with:

https://sora.unm.edu/sites/default/files/journals/auk/v115n02/front.pdf

Also note that in these hybrid zones both songs and calls are highly
variable with no consistent differences and the two species and their
hybrids cannot be reliably identified on vocalizations alone. Having birded
in both of these zones, I can vouch for having been fooled or no idea which
species or hybrid was singing until I had a visual. So it would be best to
leave unseen birds unidentified to specific species.

If anyone is interested in studying these hybrids, some great locations to
try, in addition to Mt. Walker mentioned earlier, are along Highway 123
north of Packwood and the west side of Mt. Adams including the Takhlakh and
Horseshoe Lakes area along Forest Service Road 2329 off of Forest Service
Road 23 which runs between Randle and Trout Lake. But be aware, use extra
caution when recording either of the two parent species in these areas.

Good Birding,

Alan Knue
Edmons, WA
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman11.u.washington.edu/pipermail/tweeters/attachments/20200704/2075d20b/attachment.html>