E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Troglodytes pacificus (Baird)
Pacific Wren
Family: Troglodytidae

Species account author: Jamie Fenneman

© Ted Ardley  Email the photographer   (Photo ID #8860)


Distribution of Troglodytes pacificus in British Columbia.
(Click on the map to view a larger version.)
Source: Distribution map provided by Jamie Fenneman for E-Fauna BC

Species Information

Adult
The upperparts (back, scapulars, rump, upperwings) are rich, dark rufous-brown with narrow black barring across the flight feathers (primaries and secondaries) and, usually, a series of tiny whitish or buffy spots along the tips of the greater (and sometimes lesser) upperwing coverts. The very short, slightly round-tipped tail is similarly rich rufous-brown, also with narrow black bars along its length. The underparts are rufous-brown (usually paler greyish-brown on the belly and undertail coverts) with black barring on the sides, flanks, belly, and undertail coverts. The head is rufous-brown with a paler buffy-brown supercilium, lores, chin, and throat. The iris is dark, the short, thin, pointed bill is blackish, and the legs and feet are dusky pink or flesh-pink.

Juvenile
This plumage is hed briefly during the first summer, and is typically lost by late summer (August). It is overall very similar to the plumage of the adult, but the breast and throat are variably scaled or barred with dark dusky-brown and the barring on the flanks, belly, and undertail coverts is less distinct.

Measurements
Total Length: 10-10.5 cm
Mass: 8.5-9.5 g

Source: Sibley (2000); Hejl et al. (2002)

Biology

Identification

Separated from other species of wrens with relative ease given its tiny size, very short tail, wholly dark colouration, and habitat preferences. May occasionally be confused with House Wren, but that species is larger, longer-tailed, and paler brown (often somewhat grey-tinged).

Pacific Wren is morphologically very similar to the Winter Wren of northeastern B.C., with which it was formerly lumped, and identification of non-singing or non-calling individuals (particularly out of range) would be considered very challenging, particularly given the variation within each species. Pacific Wren averages overall darker and less distinctly patterned than Winter Wren, which is slightly paler, browner, less rufescent, and more distinctly patterned. The differences are particularty noticeable on the face and throat, with Pacific Wren averaging slightly darker and more rufescent on the throat and breast, with a darker, rusty-tinged, less well-defined buffy-brown supercilium. Until the morphological differences between these two recently-recognized species are more thoroughly investigated, however, they are best distinguished by their distinctive songs and call notes.
Vocalizations

The Pacific Wren is renowned for its spectacular song, which is given frequently by the male during the breeding season. The song is a spectacular, long (up to 10 seconds), loud, complex, tumbling or cascading series of rapidly-delivered (up to 36 notes per second) ringing buzzes and hard trills; the song is longer, more rapid, more variable, and considerably more complex than the song of the boreal/eastern Winter Wren. The most common call note is a sharp timp or chat, often doubled, that is reminiscent of (but slightly sharper than) the call note of the Wilson’s Warbler; the analagous call of the Winter Wren is a hard jip that is similar in tone to the Song Sparrow and very different in quality from Pacific Wren. Also gives a rapid series of high-pitched staccato notes when agitated.

Source: Sibley (2000); Hejl et al. (2002)

Breeding Ecology

Courtship
The female is attracted to the male’s territory early in the breeding season by the male’s continuous singing. As the female enters the male’s territory, the male moves very close to the female (usually within 1 m) and continues to sing, although this singing is typically softer and more subdued than the territorial singing. This close proximity singing is also often accompanied by displays such as wing fluttering and tail cocking. The male then leads the female around the territory, displaying each nest within the territory to the female (commonly perching at the entrance of each nest and singing softly while the female perches nearby). The female then enters each nest, sometimes accompanied by the male, until one of the nests is chosen and copulation occurs. Multiple females may occupy different nests within a single male’s territory.

Nest
Multiple nests are built throughout the breeding season (early spring to mid-summer), with peak nest building activity in May and June. Although the bulk of nest building is done by the male, the female always lines the nest prior to egg laying. The well-concealed nests are placed in either existing cavities or hollows (e.g., woodpecker holes, beneath loose bark, in natural tree hollows, under overhanging banks, etc.) or placed on free-standing surfaces or structures such as logs, root wads, brush piles, and buildings; nests are rarely built in shrubs or on exposed tree branches. Most nests are built on or near the ground, usually within 2 m of the ground (although rarely as high as 7 m). The nest is a stout, domed or globular structure 7-14 cm across with an entrance hole on the side that is 1-3 cm wide. It is composed primarily of of moss, twigs, grass, and leaves and has a lining of feathers, hair, plant fibres, rootlets, needles, and strips of bark.

Eggs
A single clutch of (1) 5-7 (9) eggs is laid between late March and June and is incubated by the female for 14-17 days before hatching. Although double-brooding has not been confirmed for this species (although it is suspected in B.C.), different females within a male’s territory breed at slightly different times and, thus, eggs may be found within a given male’s territory over a prolonged period during the breeding season. The smooth, glossy eggs are whitish, usually with small reddish-brown or pale brown speckles and spots that are distributed somewhat more heavily towards the larger end of the egg. Eggs are present in B.C. between late March and late August, although most occur between April and June; later clutches generally represent replacement clutches or, perhaps in some instances, second broods (e.g., on the Queen Charlotte Islands). This species is not known to suffer from Brown-headed Cowbird nest parasitism.

Young
The nestlings are fully altricial and downy at hatching, with flesh-pink skin and short, sparse dark grey down on the head and back; the gape is bright yellow and the gape flanges are pale yellow. The young remain in the nest for 15-20 days before fledging, during which time they are tended by both parents (although the male does less feeding than the female and does no brooding). After fledging, the young remain with the parents for 1-4 weeks and are fed by both parents early in the period. The male commonly has multiple females breeding within his territory and the young from these broods fledge at intervals. This allows the male to tend to only one or two broods at any given time. Nestlings and dependent fledglings have been recorded in B.C. between early April and mid-September, although most occur between May and July.

Source: Baicich and Harrison (1997); Campbell et al. (1997); Hejl et al. (2002)
Foraging Ecology

The Pacific Wren feeds entirely on insects, spiders, and other small invertebrates (snails, millipedes, amphipods, mites, etc.) that it captures while searching continuously and methodically on or near the ground in dense vegetation. It spends a considerable amount of time exploring the crevices and microhabitats associated with fallen branches, tree trunks, and decaying logs, and sometimes ventures to the edges of creeks and streams in search of aquatic and semi-aquatic prey (occasionally even submerging the head to capture prey). Sometimes forages in more open habitats, although generally within a short distance of dense cover. Prey is typically gleaned from vegetation or other surfaces or is captured while probing cracks and crevices.

Source: Hejl et al. (2002)

Habitat


This species is characteristic of coniferous and mixed forests throughout much of the province, rarely occurring in areas of abundant deciduous trees except where small deciduous stands occur adjacent to coniferous forests. Highest breeding densities occur in forests with a dense understory and an abundance of woody debris (logs, stumps, upturned roots, slash piles, etc.) on the forest floor. It occurs primarily at middle to high elevations in the interior of the province, but is widespread at all elevations along the coast. This species is typically restricted to moist, closed forests and forest edge habitats, although migrants and wintering birds are often found in habitats away from forests such as brushy habitats (rights-of-ways, clearcuts, etc.), plantations, hedgerows, riparian strips, and suburban parks and gardens. It breeds both in mature and old growth forests as well as younger coniferous stands, and is one of few species of birds that occurs abundantly in the latter forests along the coast. Some coastal populations occur year-round on shrubby, largely treeless windswept islands, some of which are a considerable distance from the nearest forested habitats. At high elevations, breeding birds sometimes occur beyond subalpine habitats in krummholz vegetation above treeline. It is generally rare during the breeding season in the dry coniferous forests of the southern and central interior, although it occurs locally in these regions where moist gullies and ravines provide cooler, moister, and more shaded microsites with lusher vegetation.

Source: Campbell et al. (1997); Hejl et al. (2002)

Distribution

Global Range

Breeds only in western North America, from southern Alaska (including the Aleutian Islands) south through western Canada (British Columbia, southern Yukon, western Alberta) to the western United States (south to California, east to western Montana). It winters primarily along the coast, from the Aleutian Islands south to southern California, as well as locally inland east to Montana and Idaho.
BC Distribution

Breeding
Common along the entire coast, including all offshore islands. Fairly common throughout the central and southern interior of the province, although it is uncommon and local throughout most of the Chilcotin region of the central interior. It is also uncommon and local across the northern interior east to the Rocky Mountains (including their eastern foothills), becoming rare in northwestern portions of the province (north to the Yukon border).

Non-breeding
Common along the entire coast, including all offshore islands, although high elevation breeders typically move to lower elevations during the coldest months. Uncommon and local at low elevations in the south-central (Okanagan Valley, Similkameen Valley, Shuswap Lake) and southeastern (West Kootenays) portions of the interior, becoming very rare and irregular in winter farther north in the interior to Williams Lake and east to the southern Rocky Mountain Trench. It is also very rare inland along the lower Skeena River watershed on the north coast, occasionally wintering as far inland as the Bulkley Valley (Smithers, etc.) and Burns Lake areas. Casual in winter in the central interior north to Mackenzie.

Migration
The Pacific Wren is resident along the coast, although populations breeding at high elevations typically withdraw to lower elevations during the winter months. There is undoubtedly some component of migration along the coast due to the passage of interior migratory populations through this region (even if only sporadically), but this migration is not detectable given the abundance of the resident subspecies and the difficulties associated with separating the interior subspecies in the field.

East of the Coast Mountains, however, this species is a widespread and fairly common spring and fall migrant. Spring migrants appear throughout most of the interior during April, although some early migrants may appear as early as early to mid-March (even as far north as the central interior). Spring migrants typically depart valley bottom habitats during May, moving to higher elevation breeding areas as the snows melt. Fall migrants depart northern areas of the province between late July and late August, with very few individuals remaining as late as early September. In the central interior, fall migration begins in August and most birds have left this region of the province by late September (exceptionally lingering into late October or early November). In the southern interior, birds move from high elevation breeding areas to low elevation wintering habitats between August and October.

Source: Campbell et al. (1997)

Conservation

Population and Conservation Status

This is a very common and characteristic species of forested habitats along the coast, as well as in montane coniferous forests of the interior. It is not considered a species of conservation concern at either the provincial (BC CDC [Conservation Data Centre]) or federal (COSEWIC [Committee on the Status of Endangered Wildlife in Canada]) levels.

Taxonomy


Long considered conspecific with the Winter Wren (Troglodytes hiemalis) of eastern North America and Eurasian Wren (T.troglodytes) of the Old World, but these three species were separated by the AOU (American Ornithologists’ Union) in 2010 due to substantial differences in vocalizations and genetics as well as weak morphological differences. Populations of Pacific Wren breeding sympatrically with populations of Winter Wren in northeastern British Columbia, with virtually no evidence of interbreeding, were the primary driving force behind this decision.

Although this species (and its counterpart species, Winter Wren and Eurasian Wren) have represented the “typical” species in the genus Troglodytes, recent genetic evidence suggests that this group of species (the former “Winter” Wren complex) are not particularly closely related to other species in the genus Troglodytes, which includes the House Wren complex as well as a number of neotropical species of montane habitats. Because of this evidence, there are a number of authorities who recommend removing the Winter Wren complex from the genus Troglodytes and, instead, placing those species in a new genus (Nannus).

Seven subspecies of Pacific Wren are recognized, with four of these confined to the Aleutian Islands and associated areas of southwestern Alaska. Of the remaining three subspecies, two are found in British Columbia, although the morphological differences between these subspecies are relatively minor.

The two subspecies in B.C. are as follows:

Troglodytes pacificus pacificus
This is the common resident subspecies along the Pacific coast of B.C. It averages marginally darker and more rufous-tinged overall than T.p.salebrosus.

Troglodytes pacificus salebrosus (Burleigh)
This is the subspecies breeding (and wintering locally) in the interior of B.C. It averages slightly browner (less rufous-tinged), with a slightly paler and more contrasting medium to pale brown throat.

Source: Hejl et al. (2002); Toews and Irwin (2008)

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS5BYellowNot Listed
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2017. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 27/06/2017 1:48:14 AM]
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