Pacific Wren - Troglodytes pacificus
The Pacific Wren is a small dark wren (8-12 cm long, 8-12 g) with a short stubby tail typically held in an upright and cocked position, and with a short slender bill. The color is fairly uniform dark to medium brown, becoming paler on the supercilium, chin, and throat, and with dark barring on the wings, tail and underparts (belly, flanks, crissum); sexes are alike in appearance.
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Pacific Wren was formerly considered a subspecies of Winter Wren (T. troglodytes), then split in 2010 based on voice, DNA, and subtle differences in plumage (more deeply rufescent). Pacific Wrens are distinguished from other sympatric wrens by usually smaller size, much shorter tail, and fairly uniform brown coloration. Their voice is more complex and modulated, and delivered more rapidly than by the Winter Wren, such that individual notes are difficult to follow and appreciate (Hejl et al. 2002). Winter Wren reported infrequently during migration in far eastern Montana.
eBird Occurrence Map
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Note Pacific Wren and Winter Wren are both shown on this map.
In 2010, the North American populations of Winter Wren (Troglodytes troglodytes)
were split into
two separate species: Pacific Wren (Troglodytes pacificus)
(western USA and Canada);
and Winter Wren (Troglodytes hiemalis)
(eastern USA and Canada).
The map for this species-pair was generated before the split, so it shows both of the current species in a single model.
Pacific Wrens breed from southern Alaska (including the Aleutian Islands), southwestern Yukon, British Columbia, western Alberta, central Montana, and perhaps northwestern Wyoming south to central California, central Idaho, and northern Utah; an isolated breeding population occurs in central Arizona. Winter numbers are highest in the Pacific Northwest, but the species winters in most of the breeding range and sporadically in the other western states south to southern California, southern Arizona, and southern New Mexico.
Observations in Montana Natural Heritage Program Database
Number of Observations:
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(direct evidence "B")
(indirect evidence "b")
No evidence of Breeding
(regular observations "W")
(at least one obs. "w")
(Observations spanning multiple months or years are excluded from time charts)
Permanent resident in the western half of Montana.
Pacific Wrens prefer large uncut stands of old-growth and mature coniferous forests and also occur in riparian cottonwoods and aspens. In Montana they are especially common in cedar-hemlock, cedar-grand fir, and spruce-fir forests and are strongly associated with riparian areas within these forest types (Manuwal 1986, Hutto and Young 1999, Casey 2000). Snags, large trees, and downed woody debris are important components of breeding habitat. The nest substrate is highly variable and includes woodpecker cavities in trees, holes in dirt banks, niches in rotting trees, root tangles of fallen trees, clumps of hanging moss, and folds in tree bark (Hejl et al. 2002). Nesting and foraging typically occur within 2 m (6.5 feet) of the ground. In winter, Pacific Wrens use thickets in open forests and lower-elevation riparian areas in addition to large tracts of mature forests.
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Recently Disturbed or Modified
Diet is comprised of invertebrates, particularly insects and spiders, and amphipods along the Pacific coast. Stomach contents (percent of 122 stomachs) from British Columbia included 66% beetles, 51% spiders, 30% moth and butterfly caterpillars, 23% mites and ticks, 22% bees, wasps, and ants, 14% flies, 11% pseudoscorpions, 10% millipedes, and 10% harvestmen. Fruits and small vertebrates (small fish, tadpoles, small frogs) are sometimes eaten (Hejl at al. 2002).
The estimated density of Pacific Wrens along riparian corridors at Lubrecht Experimental Forest near Missoula went from 63 pairs per 40 ha in 1968 to zero in 1980 for reasons not determined (Manuwal 1986). The BBS is not a good means of measuring population trends of Pacific Wrens in Montana, probably because few roads exist in the interiors of older forests. The data from 1980-2007 indicate that numbers were relatively stable to slightly increasing survey-wide. Christmas Bird Count (CBC) data show Pacific (Winter) Wren was reported all but one winter in Montana during 1979-80 through 2009-10, and showed wide fluctuations in numbers but with no particular trend; high total count was 22 (0.0128/party hour) on 8 counts in 2001-02, low total count was 0 in 1993-94. The highest single count was seven birds at Missoula on 15 Dec 2001. CBC occurrences east of the divide are very rare. The Bozeman count has been held annually since 1949, and Pacific Wrens were found only twice, on 21 Dec 1974 and 23 Dec 2006. Similarly, one found on the Helena count on 20 Dec 1997 is the only occurrence since the first count was held in 1954. The only other CBC record from east of the divide was on the Yellowstone National Park count (centered at Gardiner) on 20 Dec 1998.
The species is double-brooded in some parts of its range. Laying of first clutches occurs from late April to mid-May, hatching from mid-May to early June, and fledging from early to late June. Flying young were seen as early as 26 June near Fortine (Weydemeyer 1975), adults tending recently fledged juveniles as late as 10 August (Montana Bird Distribution Committee 2012). Clutch size of 45 nests in Idaho was 3-7 eggs (mean = 5.7), incubation period averaged 16.5 days, fledgling averaged 16.8 days after hatching (Hejl at al. 2002).
No management activities specific to Pacific Wren are currently occurring in Montana. Maintaining large blocks of unlogged old-growth and mature forest with high densities of large trees, dying trees, and snags would be especially beneficial to this species (Casey 2000, Hejl et al. 2002); production of even-aged forest stands is detrimental, as is removal of snags and downed logs.
Threats or Limiting Factors
Pacific Wrens must have been much more abundant before the intensive logging of virgin forests that began with European settlement. Numbers can decline dramatically after even moderate levels of timber harvest (Hutto and Young 1999, Young and Hutto 2002). The species is negatively affected by forest fragmentation, logging activities that remove large trees, downed logs, and snags, and management that promotes even-aged stands (Hejl et al. 2002).
- Literature Cited AboveLegend: View Online Publication
- Casey, D. 2000. Partners in Flight Draft Bird Conservation Plan Montana. Version 1.0. 287 pp.
- Hutto, R. L., and J. S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service. U.S. Forest Service General Technical Report RMRS-GTR-32, Ogden, Utah.
- Manuwal, D.A. 1986. Characteristics of bird assemblages along linear riparian zones in western Montana. The Murrelet 67(1): 10-18.
- Marks, J.S., P. Hendricks, and D. Casey. 2016. Birds of Montana. Arrington, VA. Buteo Books. 659 pages.
- Montana Bird Distribution Committee. 2012. P.D. Skaar's Montana bird distribution. 7th Edition. Montana Audubon, Helena, Montana. 208 pp. + foldout map.
- Weydemeyer, W. 1975. Half-century record of the breeding birds of the Fortine area, Montana: Nesting data and population status. Condor 77:281-287.
- Young, J. S., and R. L. Hutto. 2002. Use of a landbird monitoring database to explore effects of partial-cut timber harvesting. Forest Science 48:373-378.
- Additional ReferencesLegend: View Online Publication
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- Hejl, S.J., J.A. Holmes, and D.E. Kroodsma. 2002. Winter Wren (Troglodytes troglodytes). Species Account Number 623. The Birds of North America Online (A. Poole, Ed.). Ithaca, NY: Cornell Laboratory of Ornithology; Retrieved 3/25/2008 from The Birds of North America Online database
- Sibley, D. 2014. The Sibley guide to birds. Alfred A. Knopf, New York, NY. 598 pp.
- Skaar, P. D., D. L. Flath, and L. S. Thompson. 1985. Montana bird distribution. Montana Academy of Sciences Monograph 3(44): ii-69.
- Skaar, P.D. 1969. Birds of the Bozeman latilong: a compilation of data concerning the birds which occur between 45 and 46 N. latitude and 111 and 112 W. longitude, with current lists for Idaho, Montana, Wyoming, impinging Montana counties and Yellowstone National Park. Bozeman, MT. 132 p.
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