No Swainson's Thrushes before May!

All Swainson's Thrushes reported before April 28 in the Pacific Northwest are probably misidentified.

There. I said it. It may not be absolutely true, but true enough that if you think you saw one before May you better make doubly sure. In fact, it is possible that many Swainson's Thrushes reported before May 8 are in error, too.

In February I wrote a blog post for Birding is Fun! titled: Ten most-misidentified birds in the Pacific Northwest. The number one identification problem mentioned by a group of knowledgeable birders was the misidentification of Hermit Thrushes as Swainson's Thrushes.

Swainson's Thrushes vacate North America in late fall and do not come back until late spring. Nevertheless, numerous beginning birders every year report Swainson's Thrushes in April and even March. Hermit Thrushes are abundant early spring migrants and winter in good numbers in wooded areas west of the Cascades. Swainson's Thrushes nest in lowlands, Coast Range, and lower mountain slopes with deciduous or mixed woods. Hermit Thrushes in the Pacific NW nest in high elevation evergreen forests from the Cascade crest eastward (also in higher Olympic Mountains of Washington).

Take a look at the photos below. Do you see why many people have trouble telling these apart?

Swainson's Thrush. 28 June 2008. Timber, Oregon by Greg Gillson.

Hermit Thrush. 17 December 2010. Hagg Lake, Oregon by Greg Gillson.

If you happen to have the National Geographic Field Guide to the Birds of North America, 6th Edition (2011), the Stokes Field Guide to the Birds of North America (2010), or the New Stokes Guide: Western region (2013) compare the Pacific coast (ustulatus) form of Swainson's Thrush and the western lowland (guttatus) form of Hermit Thrush. These are the two forms found most commonly west of the Cascades and look most alike.

Hermit Thrushes have slightly darker, rounder breast spots, and a reddish rump. Swainson's Thrushes have a pale supraloral area (the lores is the area between eye and bill, supraloral is above that). It makes the Swainson's Thrush look like it is wearing spectacles. Trouble is, this isn't that distinctive (see above photos). It doesn't help that these birds are shy and hide in the thick, shaded, understory shrubs.

East of the Cascades the subspecies look slightly less similar, but the Swainson's Thrushes east of the Cascades migrate even later in spring than those west of the Cascades.

Calls and songs are different. But Starlings and other birds can imitate the Swainson's Thrush's mellow whistled "whit" call. Hermit Thrushes give a blackbird-like chuck call.

Swainson's Thrushes reports in eBird for the Willamette Valley of western Oregon.

Notice the eBird history for Willamette Valley, 1900-2013 (above). Only a very few Swainson's Thrushes show up the first week of May; most arrive later in May. Earlier reports are either exceptionally early birds or (probably) misidentifications.

Let's look at just the last 5 years for all of Oregon.

eBird graph of Swainson's Thrushes in Oregon, 2008-2012.

There are a couple of things to note here.

1) The reports in March and early April are probably misidentified. Even if some are correct, they make up less than 1% of checklist frequency. Consider it data "noise."

2) Ignoring the early noise, the first birds for the year didn't arrive until the first week of May in 4 of 5 years. In 2008, perhaps due to weather conditions, Swainson's Thrushes arrived in western Oregon some time during the fourth week of April (April 22-30th; see the label on the above graph).

3) Notice the peak frequencies in the fourth week of May (migration) and the third week of June (territorial singing). Then notice more detections as they migrate south in September and are heard by birders at night as they fly over calling "weet."

4) A single bird with injured wing photographed in Portland in December 2008. Healthy birds are highly unlikely in winter anywhere in North America.

So that's it. Question the correctness of your identification of Swainson's Thrushes before mid-May. Try to really study both these rather common woodland and forest birds this summer and learn their calls, songs, behavior, and habitat. It's always fun to be the first one on your block (I mean, listserv) to report the arrival of a new spring migrant. It's better, though, to actually be correct.

What bird is that?... Questions and answers

Question: (June 6) "Hello Greg,
My son and I spotted a unique bird in our backyard. Can you identify this from the attached picture?
Thanks,"

Mike, location not given

Answer: I do, indeed, recognize the silhouette, Mike. That's a Northern Flicker.

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Question: (May 30) "Greg, Thanks for your web site. It's very educational and very well laid out.
I work in Salem, Oregon and generally see the same birds that I see in my Portland neighborhood, but last week, I was walking back to my office around 12:30 p.m. and heard a bird song that I'd not heard before. I immediately assumed it was a warbler and I still believe so but I cannot put the song to the bird. I have listened to every warbler song on-line that I might expect in our area and cannot match it. Can you help?
The bird was singing in a mature purple-leaved plum so not a huge tree perhaps singing8-10' up in the tree. I never saw the bird while it was singing. I cautiously circled the tree (going out into the street and across the street to try to see it, but no luck seeing the bird!). This is an area of high-density buildings both government and apartments with heavily-parked lots and lots of pedestrians. There are many mature trees and shrubs around these buildings, however. The purple-leaved plums are the street trees on this street.
The song was fairly fast-paced, sounding more like a Warbling Vireo than any warbler song that I can I.D.
It eventually flushed and flew away from me and I could see that it was warbler sized with a flash of yellow on the rump and perhaps olive. It definitely wasn't a Lesser Goldfinch or an American Goldfinch. It wasn't their song.
Any ideas? The bird was solitary and flew into a large red maple row against a large apartment. I had started to draw a crowd with my cautious movements and my staring into the tree! I thought I better get back to work so didn't see the bird again. I've never seen a Warbling Vireo as I'm mainly a back-yard birder. Could it have been a Warbling Vireo with the yellowish rump? Such a sweet but vigorous song in such an urban area.
Thanks for your help, Greg."

Steve in SW Portland, Oregon

Answer: Steve, while Warbling Vireo is certainly possible at the time and place your saw this bird, the description of the yellow rump just doesn't fit. Thus, I would suggest that it is the most abundant migrant in western Oregon during the spring. Guess what? It has a yellow rump in its name! There are two races of Yellow-rumped Warblers and both migrate through the Pacific NW, Myrtle breeds farther north and starts migrating as early as March, and Audubon's starts in May, but both occur through spring. The voices, both calls and songs, are different. Many recordings are of the more widespread (common in the East) Myrtle Warbler. So make sure you are listening to the correct bird recording. Listen to the Audubon's Yellow-rumped Warbler songs on Cornell's "All About Birds" online field guide site.

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Question: (June 3) "Hello Greg - I'm going nuts trying to discover the author of a fantastical call that I hear all day, every day right now. Here's my best description of it:
A single high-pitched, upwardly rising note, that spirals upward in three "loops", ending in a shimmery, echoing glissando effect. I am referring to this unseen bird as the Ventriloquist due to the amazing shimmery finish at the end, like water ripples spreading. It seems that between these beautiful calls, the bird hops around and makes a tiny, quiet, single "po" call. Then the upward-spiralling call again and again. It's so beautiful. I recall hearing it all last Summer and it just started again a few weeks ago.
Today I saw a classic LBB (little brown bird!) in the vicinity of the call... Looked just like a Hermit Thrush or so, with large eye and needle-sharp insectivore bill. Buff color with some speckles at the throat and barely lighter buff belly.
Any hope of IDing this masterpiece? I am always trying to get a glimpse of the singer but the bird is very, very shy. I live near a forested wetland with tons of cover. Lots of Robins around and lots of other birds too. (blog link below) If you can help me, it would be just wonderful. If not, I totally understand!! Thanks for reading this. Sincerely,"

Bonnie in Quilcene, Washington
http://back2theland.blogspot.com

Answer: What a beautiful and accurate description of the song of Swainson's Thrush! Most people have a very difficult time describing a bird song or call, but you nailed it, Bonnie! The spotted thrush with buff underparts is Swainson's and not Hermit Thrush. Hermit Thrushes have more gray underparts and breed in the high mountains (spruce and true fir) and those that breed in Alaska will winter in your lowland woods. Hermit have rusty rump and uppertail. Swainson's Thrushes are rare north of Mexico before mid-April and head back down there in September when their distinctive "whit" and "heep" calls are heard overhead during their night migration. Swainson's Thrushes may be one of the most abundant birds in riparian foothill clear cut regions of red alders before the Douglas fir grow up too much. The other abundant birds in Swainson's Thrush habitat are Wilson's Warblers and Warbling Vireos. Listen to Swainson's Thrush song in Cornell's "All About Birds" field guide.