Adult The upperparts are drab grey-brown with fine dark and pale buffy or whitish speckling on the back, scapulars, and upperwing coverts. The rump and uppertail coverts are brighter tawny-buff to cinnamon with speckles similar to those on the rest of the upperparts. The tail is drab brown or grey-brown with narrow dusky-grey bars, and there is a relatively broad blackish subterminal band and buffy terminal band on the outer feathers. The underparts are mostly dingy whitish, with narrow grayish streaks on the upper breast and a buffy or pinkish-cinnamon wash on the belly, sides, flanks, and undertail coverts. The undertail coverts also sport dark chevron-shaped marks. The crown and nape are drab grey-brown like the upperparts and are similarly speckled with dark and light specks. The lores and ear coverts are similarly drab grey-brown, separated from the crown by a faint paler buffy supercilium. The cheeks, chin, and throat are drab grayish to dingy-white, with fine grayish streaks on the throat. The iris is dark, the relatively long, slender, slightly down-curved bill is dark grey with a paler base to the lower mandible, and the legs and feet are dusky or dark grey.
Juvenile This plumage is held until the fall of the first year. It is very similar to the adult plumage but is paler and buffier, with few or no speckles on the crown. Juvenal plumage appears overall plainer and less contrasting than the adult plumage.
Measurements Total Length: 15-15.5 cm Mass: 16-17 g
A combination of the shape and structure of this species, as well as its drab brown colouration and typical rocky habitat render it nearly unmistakable within B.C. The only other remotely similar species inhabiting similar habitats, the Canyon Wren, is noticeably darker and richer chestnut-brown with a sharply contrasting white throat and breast. These two species should not be easily confused.
The male’s song consists of a jangling, ringing series of phrases of 3-5 repeated notes, with the notes within each phrase changing and pauses of several seconds between each phrase: keree-keree-keree, tweer-tweer-tweer-tweer, chrr-chrr-chrr, prree-prree-prree. The call note, which is given by both sexes, is an emphatic, ringing, two-noted tick-ear, usually produced by the bird during a deep, exaggerated bob.
Courtship The male’s song functions as the primary means of courtship in Rock Wren, although courtship-feeding has also been observed. During singing, the male typically sings from a high, exposed rock outcrop within his territory or from within vegetation to a height of 6 m. This species is monogamous throughout the breeding season.
Nest Nest building begins early, shortly after arrival on the breeding grounds. Both sexes participate in the construction process, which takes 3-5 days to complete. The nest itself is usually placed in a cavity or a sheltered, secluded location such as beneath an overhanging rock, within a crack in loose talus, or in a crevice in a cliff or rock face. This species sometimes places its nest in subterranean mammal burrows (e.g., ground-squirrels) or in crevices in buildings or structures (e.g., dams). The nest is a shallow cup ~9 cm across. It is composed of grass, sticks, strips of bark, moss, hair, and occasionally fresh plant material and is lined with rootlets, hair, wool, and spider silk. It is typically situated on a foundation of stone and may contain tiny pebbles in the lining. The Rock Wren has an unusual habit of often constructing a narrow “pathway” or “pavement” of stones and other material (small bones, feathers, small bits of garbage, twigs) leading up to the edge of the nest.
Eggs Clutches of late (4) 5-6 (10) eggs are laid following nest completion. In B.C., eggs have been documented between late April and late July, although May is likely the primary month for eggs in the province. The eggs are smooth, glossy, and whitish with sparse, fine reddish-brown to buffy-brown or pale purplish speckling and blotches. The incubation period is 12-15 days, and most eggs likely hatch between late May and mid-June. Only the female incubates the eggs, often fed by the male. This species appears to be double-brooded in B.C., producing two clutches in some areas. This species is an occasional host for Brown-headed Cowbird parasitism, but this has not been recorded in B.C.
Young Young may appear in B.C. as early as late May, but most likely appear in June and July. After hatching, the hatchlings remain in the nest for 14-16 days before fledging and are tended by both parents. The altricial young have pale pinkish skin and patches of yellowish-white down; the mouth is pinkish-yellow. Once they have left the nest they continue to follow the female around the territory as a “family group” before becoming independent. Parental care of late broods has been recorded in B.C. into August and even early September.
Source: Baicich and Harrison (1997); Campbell et al. (1997); Lowther et al. (2000).
The Rock Wren feeds primarily on insects and other arthropods such as grasshoppers, crickets, ants, aphids, leafhoppers, beetles, and spiders, and is known to occasionally consume small lizards. It hunts primarily along the ground and on the surfaces of rocks and boulders, commonly entering cracks or crevices in loose rock or probing into clumps of grass in search of prey. It generally picks prey directly from the substrate and rarely captures insects in flight. It occasionally consumes aquatic insects such as dragonfly larvae, and has been known to forage in a creeper-like fashion along the bark of trees.
Source: Lowther et al. (2000).
The Rock Wren is closely, though not exclusively, tied to open, rocky habitats such as exposed rock outcrops, canyons, talus slopes, rock piles, coulees, quarries, roadside cuts, and fractured cliffs during the breeding season. The presence of cracks, crevices, and other fractures appears to be highly important in the habitat throughout the year, although it is especially critical for breeding birds. Some local populations breed in and around human structures such as dams, where they are able to locate narrow cracks and crevices that mimic the conditions that are found in natural breeding habitat. This species also breeds occasionally in open, rocky, arid shrub-steppe habitats or clearcuts away from outcrops. Breeding populations occur from the lowest elevations to the high alpine, where high elevation scree and talus slopes provide conditions similar to those found in the arid valley bottoms. Wintering birds are less strictly tied to rock habitats than breeders but still prefer to inhabit these conditions when they are available (especially in the interior). On the south coast, most wintering individuals are found in tidewater habitats along the immediate shoreline, usually in the vicinity of breakwaters, coastal rip-rap, rock piles, or piles of driftwood that provide crevices for retreat. Migrants are occasionally encountered in unusual habitats, such as on open grassy prairie around ground-squirrel burrows and in brushy habitats alongside an airfield.
Source: Campbell et al. (1997); Lowther et al. (2000).
Breeds throughout the western United States (east to the Great Plains) and into western Canada (southern B.C. east to southern Saskatchewan). Breeding populations also occur south through northern and central Mexico, with isolated and disjunct population farther south from extreme southern Mexico south to Nicaragua. Most wintering individuals occur south of northern California, Utah, and Oklahoma (with all southern populations essentially resident), although occasional individuals winter north to southern Canada. It is a casual vagrant to eastern North America.
Breeding This species is uncommon to fairly common, but always highly local, across the southern interior of the province, from the Coast and Cascade Mountains east to the Rocky Mountains and north to the Williams Lake and Revelstoke areas. The largest numbers are found in the Okanagan Valley and associated basins. It is rare along the crest and eastern slopes of the Coast Mountains at least to the Bella Coola area, and breeding-season records from the Cariboo Mountains (east of Quesnel) suggest a small local population may breed in that area as well. Multiple breeding season records along the Rocky Mountains as far north as Pink Mountain similarly indicate that this species may breed at low densities well into northern B.C. In southwestern B.C., this species is known to have bred on at least one occasion on southeastern Vancouver Island (Genoa Bay, 1970) and additional breeding season records, often of singing males, from suitable habitats in the Gulf Islands and Vancouver Island suggest that a few pairs may breed annually in southwestern B.C. The Rock Wren tends to occur at relatively low densities across much of its breeding range and is often overlooked.
Winter Rare in winter in the southern Okanagan Valley, and very rare in the northern Okanagan Valley. It is casual in winter farther north to the Kamloops area. On the south coast, it is very rare in winter on southeastern Vancouver Island and in the Lower Mainland, principally the Victoria and Vancouver regions.
Migration and Vagrancy Scarce and uncommon spring and fall migrant through southern B.C., but probably largely overlooked. Spring migrants begin to arrive in the southern interior in late April or early May (occasionally as early as March), with the first individuals usually arriving in the Okanagan Valley. Fall migration is more difficult to ascertain, as numbers gradually decline through August and September as birds leave their breeding territories. The breeding population is more or less absent from the province by early October, although lingering migrants are sometimes detected across the southern interior as late as November. It is very rare and irregular during migration in the Georgia Depression area of the south coast (April-June; September-November). Accidental on the north coast (Prince Rupert) in May and in the west-central interior (Ootsa Lake) during the breeding season.
Source: Campbell et al. (1997).
Population and Conservation Status
Populations in B.C. are not declining, and this species is not considered a conservation concern at either the provincial (B.C. CDC [Conservation Data Centre]) or federal (COSEWIC [Committee on the Status of Endangered Wildlife in Canada]) level. There is some indication that the range of this species may be expanding northward on the province, as it has been recorded from the Chilcotin, Coast Mountain, and northern Rocky Mountains only relatively recently. It is possible, however, that the apparent spread of the species in B.C. may be an artifact of observers detecting it in areas where it occurs in very low densities or in remote habitats (e.g., alpine scree). Nonetheless, it is difficult to believe that it would not have been detected in some of the low elevation portions of its range if it were present historically and as a result it does appear that the increase in the bird’s distribution in the province may at least partially be due to an actual increase in the population.
Source: Campbell et al. (1997).
There are currently eight recognized subspecies of Rock Wren, although only one of these subspecies (S.o.obsoletus) occurs north of Mexico (ranging into B.C.). Many of the southern subspecies are isolated and disjunct from the remainder of the species’ range, often on islands. The Rock Wren is not particularly closely related to other wrens, and may be a sister taxon to the entire rest of the family Troglodytidae.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2012. 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:
5/18/2013 10:48:26 AM]
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