Sunday, November 27, 2011

Learning about birds... at your feeder

Spotted TowheeMale Spotted Towhee, Beaverton, Oregon, 27 November 2011 by Greg Gillson.

 

For improving one's birding skills, Kenn Kaufman (Kaufman Field Guide to Advanced Birding) recommends a bird feeder as a learning tool. Even a common species observed closely over time can teach about age and gender differences, molt and plumages, hybridization, and individual or population variation. Learning how to observe these items on common birds will let us more quickly and accurately identify rare birds--a source of joy and excitement for many birders.

Earlier this year I learned something very interesting by observing the birds at my feeder. Although perhaps not surprising, I observed a subspecies of Spotted Towhee not previously documented in western Oregon. I wrote about it here: (Barely spotted towhee gets super spotted visitor).

Now that I am attune to this particular ID challenge, I was ready today when I again spotted an unusual towhee visitor to my feeder. The top photo shows a resident male Spotted Towhee, typical of those found in western Washington and Oregon, the so called Oregon Towhee (Pipilo maculatus oreganus).

The ID of the above bird is straightforward. Compared to all other populations it has fewer spots on its scapulars and wings. The rufous sides are darker than other populations. Finally, the spots on the undertail are very small, perhaps restricted to only the outermost tail feathers of each side of the tail.

Compare the bird above with the bird below, seen about 15 minutes apart in the same tree--photographed through my very dirty window!

 
Spotted TowheeMale Spotted Towhee, Beaverton, Oregon, 27 November 2011 by Greg Gillson.

 

This bird is paler orange on the side and undertail coverts. It has more and larger spots on the scapulars and wings. Obviously, the white tail spots take up more than half the tail and are spread out on at least three of the outer tail feathers.

This bird matches one of the "Interior" forms of Spotted Towhee. The new National Geographic Field Guide to the Birds of North America, Sixth Edition has range maps showing the various subspecies of Spotted Towhees.

Without a specimen to measure fine variations, it is only speculation as to which exact subspecies may be represented. And due to individual variation, even a specimen may not be unequivocally decisive in this matter. However, it is sufficient to separate the Pacific form (to which the Oregon Towhee belongs) from the Interior form to report this to eBird. In fact, birders in Washington are noting the winter influx of the Interior form of Spotted Towhees into western Washington where, as in western Oregon, they were previously undocumented.

These new winter distribution records are found, not from scientists studying specimens or conducting field research, but by amateur bird watchers at their backyard feeders!

What's in your feeder?

7 comments:

  1. Addendum: Adding a subspecies or population group to your eBird checklist.

    When submitting species to your list, eBird presents you with a list of likely species based on your location and month of the year. Two options are check boxes to "Show Rarities" and "Show Subspecies." I suggest keeping the subspecies box checked (eBird remembers for future sessions).

    If a subspecies you wish to enter doesn't show on the list, follow these procedures to see if it exists at all.

    Choose "Add Species." Type in the generic name of the species. For instance, type "towhee" and some of the options that come up include:
    Spotted Towhee
    Spotted Towhee (Pacific)
    Spotted Towhee (Rocky Mtn.)
    Spotted Towhee (Olive-backed)
    Spotted x Eastern Towhee (hybrid)
    Spotted/Eastern Towhee
    towhee sp.

    Use this technique if you wish to report subspecies for white-cheeked geese, flickers, juncos, fox sparrows, brant, yellow-rumped warblers, scrub jays, marsh wrens, Hutton's vireos, and other major field identifiable forms.

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  2. I was going to say "That bottom photo looks like the Spotted Towhees I see in Utah and Idaho." Good stuff Greg!

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  3. Great post - very helpful!

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  4. Greg,

    I admire your efforts to encourage folks to take a second look at common birds and to take note of the range of variation they display. Spotted Towhees are a great case study in this regard as there is much variation in the amount of spotting above and the darkness or lightness of the rusty orange below.

    That said, I don't think it's accurate to suggest that until recently non-oregonus Spotted Towhees were "previously undocumented" in w. Washington and w. Oregon. I've engaged in many discussions about the variation and subspecific origin of the handful of heavily-spotted Spotted Towhees that I and others see every year west of the Cascades. Just last March I photographed a heavily-spotted adult male Spotted Towhee on Sauvie Island n. of Portland. (See photo #16 at this link: http://www.birdfellow.com/photos/thumbnails/120-ofo-sauvie-island-field-trip-19-march-2011).

    I think you'll agree that the bird in my photo is very similar if not nearly identical to the heavily-spotted individuals in the photos you've shared on this website. Such birds are few in w. Oregon, but not all that rare.

    Jon Dunn, whose keen interest in Spotted Towhee taxonomy and variation spawned the extensive subspecific treatment in the more recent editions of the National Geographic Guide, will tell you that we still have much to learn when it comes to understanding the variation that each subspecies might show and where their respective ranges begin and end. I don't think it is safe to start assigning these heavily-spotted birds to a particular subspecies, as there are several subspecies populations that these birds may originate from.

    When we see a heavily-spotted Spotted Towhee in the Willamette Valley, do we know for sure that we are not looking at the most heavily-spotted expression of the subspecies "oregonus," an "oregonus X interior form intergrade, or a "pure" representative of one of the interior populations?
    We can speculate, but I contend that assigning a particular individual to a particular subspecies is dicey. Further, to encourage folks to make such assignments in their eBird reporting is probably adding an unnecessary layer of potentially incorrect information to an already imperfect database.

    Dave Irons
    Content Editor BirdFellow.com

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  5. Thanks for the well thought-out comments, Dave. By "undocumented" I meant prior to my earlier post this spring (I am aware of your subsequent discussions later in March), but primarily in "Birds of Oregon: a general reference" (2003), and previously, "Birds of Oregon" (1940) and "Birds of Washington State" (1954).

    I agree that you can't assign exact subspecies to the visitor. However, having paid attention, I disagree that there is any likelihood of this bird being at the extreme edge of range of variation for oreganus subspecies. White tail spots on 3 outer feathers covering more than 2/3 the tail for the visitor, versus 1 tail spot in less than 1/4 of the lenght of the tail for oreganus, without the scapular spotting, side coloration, and under tail covert coloration.

    At any rate, our discussion can only bring attention to this possible issue of Rocky Mountain type Spotted Towhees wintering west of the Cascades when none are (scientifically) "documented." Our interest as birders will probably NOT lead to any scientific investigation.

    But, keen observation--at all of nature--is something I know we both encourage.

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  6. All of the popular field guides show the variation in Spotted Towhees.

    Sibley (2000) and the National Geographic 3rd edition (1999) did so less specifically.

    The Stokes guide (2010) specifically names all subspecies. The new National Geographic 6th Edition (2011) names and maps all subspecies and clearly delineates between the "coastal" group and the "interior" group.

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