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Thryomanes bewickii (Audubon, 1827)
Bewick's Wren; Bewick’s Wren
Family: Troglodytidae

Species account author: Jamie Fenneman
Introduction to the Birds

Photograph

© Ted Ardley     (Photo ID #8196)

Map


Distribution of Thryomanes bewickii 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, including the back, scapulars, rump, and wings are brown, with fine dusky bars across the flight feathers. The relatively long, slender, rounded tail is blackish-brown, with broad greyish-brown bars on the central feathers and small (but distinct) white spots or bars at the tips to the outer feathers; the tail is commonly held cocked. The underparts are pale greyish with a brownish wash on the flanks and narrow dark brown bars on the greyish-white undertail coverts. The crown and nape are brownish (similar in tone to the upperparts) and the ear coverts are greyish-white and faintly mottled with darker dusky-grey, usually showing a thin, inconspicuous whitish crescent below the eye; the lores are dusky-grey. A long, bold, whitish supercilium extends from the base of the bill back to the sides of the nape, and is separated from the greyish ear coverts by a brownish post-ocular stripe that extends from the eye back along the top of the ear coverts. The chin and throat are greyish-white, slightly paler than the remainder of the underparts. The iris is dark, the relatively long, very slender, slightly decurved bill is greyish to blackish with a paler grey or horn-colored base to the lower mandible, and the legs and feet are dark greyish to paler brownish-grey.

Juvenile
This plumage is held until late summer (August) of the first year. Juveniles are similar to adults, but the throat and underparts are faintly mottled with dusky-grey (heaviest and darkest on the throat and breast), the sides and flanks have a more extensive and buffier wash, and the crown, nape, and back are finely and faintly barred with dark grey.

Measurements
Total Length: 13-13.5 cm
Mass: 7.5-12 g

Source: Kennedy and White (1997); Sibley (2000)


Biology

Identification

The size, structure, plumage patterns, and behaviour of the Bewick’s Wren are all highly diagnostic, and it is unlikely to be confused with any other wren in the province.
Vocalizations

The male’s song is highly variable, including a variety of thin, rising buzzes and slow trills, although certain patterns dominate within the British Columbia portion of its range. The song usually begins with several short, sharp notes and ends with a long, high-pitched trill; typical variations include t-t zree drr-dree tututututututu and tick-r tick-r treeeeeeeeee. The introductory notes and overall cadence of the song are reminiscent of the song of a Song Sparrow, while the terminal trill may recall the song of a Spotted Towhee. Singing begins very early in this species, and populations on the south coast of B.C. are singing regularly by late January or February. Calls include a harsh, drawn-out shreee or jree-jree, a soft, dry jik, and a high, rising zrink.

Source: Kennedy and White (1997); Sibley (2000)

Bird calls (and videos) from Cornell's Lab of Ornithology
Breeding Ecology

Courtship
Courtship and the formation of pair bonds occur very early in the year, usually in February or March. Pre-copulatory displays by the male include calling, mate-feeding, and spreading the tail and turning from side to side to expose the white spots in the outer tail feathers; the female may respond to these displays by wagging her tail back and forth or by giving soft calls. This species is primarily monogamous.

Nest
The nest is constructed by both sexes, with nest-building activities commencing as early as February or March in B.C. Most nests are constructed in 2-8 days, although poor weather may delay completion of the nest for up to 3 weeks. The nest is usually placed low to the ground, usually at a height of 1-2 m (occasionally as high as 10 m or as low as ground-level). The nest is a bulky cup that is typically placed in a cavity or on a sheltered shelf. This species is opportunistic in its choice of nesting substrates, and the location of nests is highly variable; nests occur in both natural (woodpecker cavities, hollows in snags, tree stumps, upturned tree roots, rock crevices) and artificial (buildings, barns, sheds, posts, abandoned automobiles, junk piles, nest boxes, brush piles) settings. The nest itself is constructed of a wide variety of materials such as dry grasses, twigs, wood chips, rootlets, moss, leaves, spider webs, feathers, wool, and hair and lined with finer materials; this species often incorporates whatever materials are available into its nest. The dimensions of the nest are somewhat dependent on the dimensions of the nesting chamber, but the cup of most nests is 5-6.5 cm across and 3.5-5 cm deep.

Eggs
This species appears to be double-brooded in B.C. The first clutch of (3) 5-7 (11) eggs is laid in late March or April and is incubated by the female for 14-16 days before hatching; a second clutch is sometimes laid in May or June. The smooth, slightly glossy eggs are white with very fine reddish-brown speckles and a few purplish-brown splotches (larger markings concentrated around the larger end of the egg). Eggs occur in B.C. from mid-March to mid-July. This species is a relatively uncommon host for Brown-headed Cowbird parasitism.

Young
The young are altricial and largely naked upon hatching, with pink skin and a few small patches of down. The young remain in the nest for 14-16 days before fledging, during which time they are tended by both parents. After fledging, the young remain together as a group and are fed by both parents for ~2 weeks before dispersing and becoming independent.

Source: Baicich and Harrison (1997); Campbell et al. (1997); Kennedy and White (1997)
Foraging Ecology

This species usually forages low in shrubs and trees, commonly within dense vegetation and therefore difficult to observe (although it also forages regularly in exposed situations as well). It feeds on a wide variety of invertebrates, especially adult and larval insects and spiders, which it gleans from leaves, branches, and twigs or probes from crevices in the bark. It often forages on the ground, where it hops about and picks prey from the surface of the soil; it often flips fallen leaves aside to access the prey that is hidden underneath. It rarely hawks flying insects or captures prey by hover-gleaning. In suburban and rural areas, it is commonly attracted to bird feeders, especially where suet is offered.

Source: Kennedy and White (1997)

Habitat


The Bewick’s Wren exploits a wide range of brushy habitats and open wooded areas at low elevations in southwestern B.C., but tends to avoid closed forests. Typical habitat includes brushy hedgerows, brambles, riparian thickets, estuarine thickets, forest edges, Garry Oak woodlands, and the brushy understory of open coniferous and mixed forests. It is a common inhabitant of suburban parks, gardens, and backyards where it nests and forages in hedges and ornamental shrubbery. In the Okanagan Valley of south-central B.C., this species has been found primarily in brushy riparian areas.

Source: Campbell et al. (1997)

Distribution

Global Range

Largely resident along the Pacific coast of North America from British Columbia south to Baja California, as well as throughout the southwestern and south-central United States east to Texas, Arkansas, and Missouri and north to Wyoming; northernmost populations on the Great Plains largely withdraw in winter. Small numbers also breed in the eastern United States (Appalachian region), but these are largely extirpated. It is also resident throughout much of northern and central Mexico.
BC Distribution

Resident
Fairly common to common on the south coast, including southern and eastern Vancouver Island (north to Comox), the Gulf Islands, and the Lower Mainland (primarily east to Hope); uncommon on the Sunshine Coast (north to the Sechelt Peninsula) and on eastern Vancouver Island from Comox north to Sayward. Very rare throughout the year in the southern Okanagan Valley north to Kelowna, and recently documented breeding in this area (Vaseux Lake, 2008); also recently (2010) discovered in small numbers during the breeding season along the lower Kettle River east of the Okanagan Valley (e.g., Grand Forks, Midway), including at least one confirmed breeding record.

Vagrancy
Very rare year-round (primarily from spring through fall) on northern and western Vancouver Island, as well as during the summer north along the mainland coast to Powell River and inland to Pemberton and Manning Provincial Park.

Source: Campbell et al. (1997)

Conservation

Population and Conservation Status

Although breeding populations in the eastern United States have declined dramatically over the past century, populations in western North America, including those in B.C., are either stable or increasing. This species is very common throughout much of its distribution in the province, particularly on southern Vancouver Island and the Gulf Islands, and adapts well to suburban and agricultural development as long as some brushy vegetation is retained. In the Okanagan and Kettle River valleys of the southern interior, this species was first reported as recently as 2006 but only two years later was found breeding in southern portions of the Okanagan valley. There are currently only a small number of records of this species in the southern interior (<10-15 records), but its recent expansion into eastern Washington (the source of the Okanagan birds) and the abrupt increase in records in the south-central interior over the past 2 years, suggest that this species is continuing its expansion north into the interior of B.C. and may eventually become a regular component of that area’s avifauna. This species is not recognized as a species of concern by either the B.C. Conservation Data Centre (CDC) or COSEWIC (Committee on the Status of Endangered Wildlife in Canada).

Source: Kennedy and White (2007)

Taxonomy


A total of 20 subspecies are recognized within this species, one of which is now extinct, with 17 of these occurring in the United States and Canada (the remaining three are confined to Mexico). Only T.b.calophonus Oberholser, which is a relatively brown subspecies of the Pacific coast from B.C. to northwest Oregon, is found in British Columbia. Populations of calophonus occurring in southwestern B.C. and northwestern Washington may average slightly redder than elsewhere in the subspecies’ range and have sometimes been recognized as a distinct subspecies (A.c.“ariborius”). Similarly, populations of calophonus in central Washington, which occasionally occur north into the Okanagan Valley of B.C., may average slightly more olive-brown and have been recognized as subspecies T.b.hurleyi; both ariborius and hurleyi are poorly marked, however, and the plumage differences, if they exist at all, are too slight to warrant recognition my most current authorities.

Source: Kennedy and White (1997); Pyle (1997)

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)		COSEWIC
NativeS4YellowNot Listed



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