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Pacific Wren

By Ben Young

Birders have enjoyed much activity in the world of the wren in recent years, months, and weeks. Over a year ago I found myself chasing a Sinaloa Wren, originally found near Patagonia, AZ, a bird that would later be accepted as a new ABA record. More locally, Montana birders were treated to the state’s first accepted record of a Carolina Wren, which remained for some time this spring near Arlee, MT.

Most recently, bird listers picked up an extra species on the state list when the American Ornithologists’ Union split the Winter Wren (Troglodytes troglodytes) into two species this past July: Pacific Wren (Troglodytes pacifica) and Winter Wren (Troglodytes hiemalis). New range maps for the two species (below) show the western terminus of the Winter Wren’s range to presumptively extend into eastern MT (Sibley 2010). Overlap in the breeding ranges of the two formerly recognized subspecies may be found in eastern British Columbia. A major impetus for the split likely came from research by Toews and Irwin (2008), who found that hybridization of eastern and western birds did not occur in this region of breeding range overlap, citing song type differences and nuclear DNA divergence as evidence that the two species are reproductively isolated.

So, why not make the most of the change and go find a “new” bird in the Flathead Valley? You’ll want to head for the understory of moist coniferous forest, the kind easily found along the foothills of the Swan Range, or along the lower portions of Going to the Sun Road, especially near Avalanche Creek. As for detection, an apt description for this species was penned by Gabrielson and Jewett (1940)—“a pert little bit of brown fluff” and “a mouselike mite … that … mounts to the top of a convenient stump and bursts forth in the most amazing, loud, clear song that ever came from a brown protuberance.” Such a song (up to 36 notes/sec according to Sibley), consists of up to 30 uniquely organized and repeatable sequences or types for the Pacific Wren, compared to only 2 types for the eastern Winter Wren (Kroodsma 1980), and will no doubt stop you in your tracks the first time you hear it. Described as the bird at the pinnacle of song complexity, the Pacific Wren boasts “the longest definitely reiterated” song pattern among North American birds (Hartshorne 1973).

When not singing from a fairly prominent perch, Pacific Wrens are fairly reclusive, remaining exposed for brief moments only to retreat to thick cover. I recall chasing the perpetrator of a sharp coupling of chip notes, as well as a quick sequence of high staccato notes coming from within an English ivy-laden understory of a mixed coniferous forest in western Oregon during my fledgling birding days. After ten minutes of seeing nothing, my eyes caught a dark brown speck pop out of the ivy. Just as soon as my binoculars were mounted to my eyes, it was gone. Convinced I had seen something new in my neighborhood, I continued this cat-and-mouse game for nearly a half hour, until I finally decided to just wait and watch, rather than chase. Before long the bird alit on an old hemlock stump—it was a Pacific Wren—and then proceeded to give me a physics lesson on resonance as it burst forth in singing. I had become familiar with its song, but I’d never been acquainted with its call.

Plumage characteristics of this diminutive and nervous bird may be closely admired by a patient, quiet observer. I’ve had numerous occasions of Pacific Wrens approaching within arm’s reach, revealing a dark, rich brown interrupted by darker barring on wings, flanks, and tail, with a distinct supercilium. Its short tail is often held erect as it flits in and out of nooks and crannies in search of beetles, flies, spiders, and caterpillars.

REFERENCES:
* GABRIELSON, I. N., AND S. G. JEWETT. 1940. Birds of Oregon. Oregon State College, Corvallis. (Reprinted in 1970 as Birds of the Pacific Northwest by Dover Publ., New York.)

* HARTSHORNE, C. 1973. Born to sing. An interpretation and world survey of bird song. Indiana University Press, Bloomington.

* KROODSMA, D. E. 1980. Winter Wren Singing Behavior: A Pinnacle of Song Complexity. Condor 82,357-365.SIBLEY, D. 2010. New draft range maps for Winter Wren. Accessed Online 18 Aug. 2010: http://www.sibleyguides.com/2010/08/new-draft-range-maps-for-winter-wren/.

* TOEWS, D.P., IRWIN, D.E. 2008. Cryptic speciation in a Holarctic passerine revealed by genetic and bioacoustic analyses. Molecular Ecology, 17(11), 2691-2705.

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