Winter Wren Troglodytes troglodytes This information was scanned from The Birds of British Columbia (Campbell et al.), Volume III, pages 320-326. Volumes I, II and III of The Birds of British Columbia can be ordered electronically at: orders@ubcpress.ubc.ca from UBC Press in Vancouver, British Columbia.

 

Range Resident from coastal southern and southeastern Alaska south along the Pacific coast to central California and the southern portions of the interior of British Columbia. Breeds from northern British Columbia through the forested parts of Canada to Newfoundland, south into northwestern Oregon and northern Idaho in the west, and Georgia and Tennessee in the east. Winters within, but mostly south of, the breeding range, including the southern United States. Also occurs in Eurasia and northwestern Africa.

Status On the coast, fairly common to common resident in southwestern British Columbia, including the Georgia Depression Ecoprovince and Western Vancouver Island, Queen Charlotte Islands, and Southern Mainland Coast of the Coast and Mountains Ecoprovince, becoming uncommon along the Northern Mainland Coast of that ecoprovince, including offshore islands other than the Queen Charlotte Islands.  In the interior, fairly common resident in the Southern Interior and the Southern Interior Mountains ecoprovinces; uncommon migrant and summer visitant, and locally very rare throughout the year, in the Central Interior and Sub-Boreal Interior ecoprovinces; very rare migrant and summer visitant to the Northern Boreal Mountains and Boreal Plains ecoprovinces; casual in the Taiga Plains Ecoprovince.  Breeds.

Status Change Munro and Cowan (1947) did not include the Cariboo and Chilcotin areas of the Central Interior, or northeastern British Columbia north of the Peace Lowland, within the range of the Winter Wren. It is now known to be a local resident at lower elevations and a fairly common summer visitant in the subalpine forests of the Central Interior, and a scarce summer visitant to the Taiga Plains and eastern Northern Boreal Mountains.

Nonbreeding The Winter Wren is widely distributed in forested habitats throughout much of the province. It is most numerous and occurs throughout the year in the dense coniferous forests along the coast. East of the coastal mountains, it occurs in forested areas in much of the southern and central portions of the interior east to the Rocky Mountains and north in local populations to the Tatshenshini River, Liard River, and Fort Nelson areas. It is sparsely distributed in northern regions. The highest numbers in winter occur in the Georgia Depression and adjacent mountain slopes. Root (1988) notes that the Winter Wren winters mainly in areas that receive an annual precipitation of at least SO cm, which occurs on most of the coast. On the coast, the Winter Wren has been recorded at elevations from sea level to 1,S00 m. In the interior, it has been recorded up to 2,250 m in the Southern Interior Mountains and 1,950 m in the Central Interior. Although it uses a wide range of habitats, it is seldom found more than a few metres above ground. On the coast, the Winter Wren prefers forested habitats where the forest floor is shaded and has "old-growth" characteristics such as ground litter and fallen trees in various stages of decomposition, especially where the skeletons of upturned root-masses are a prominent landscape feature, and where mosses are the dominant ground vegetation. It also occurs in areas of dense brush and shrubs associated with the edges of human-made corridors, in thickets at the edges of wetlands, and in more open forests with a shrubby ground layer. On treeless offshore islands, it frequents dense, wind-pruned, shrubby vegetation. Along coastal beaches, it uses piles of driftwood above the upper tideline as foraging habitat. On the west coast of Vancouver Island, Bryant et al. (1993) found the Winter Wren present in 96%: (n = 71) of old-growth plots, 69% (n = 36) of 50- to 60-year-old forest plots, 64% (n = 36) of 30- to 35-year-old forest plots, and less than 25% of plots in forests that were less than 21 years old. In Pacific Rim National Park, on the other hand, it was common in a 2-year old clearcut and in a 24-year-old forest replanted after logging (Roe 1974). In the interior, the Winter Wren occurs in more dispersed populations, especially where old-growth forest occurs. At lower elevations, dense woods in moist ravines or gulleys that have thick underbrush are used. At higher elevations, dense spruce and fir forests are used, including krummholz habitat at the timberline. An exception is the Douglas-fir-ponderosa pine forests of the southern valleys, where the Winter Wren occurs mainly in migration; even there it may be resident in shaded, cooler gullies where western redcedar is present. The Winter Wren, a versatile little bird, also occurs at the edges of clearings of powerline rights-of-way, in logging slash, and in shrubbery of parks, golf courses, and gardens. During the winter it finds sheltered roosting sites in old woodpecker nest cavities, bird and mammal burrows, abandoned or open outbuildings, and even crevices in occupied homes. Most of the population along the coast and in the Southern Interior and Southern Interior Mountains is resident, but elsewhere in the province this wren is migratory. Spring migration is not discernible in the Georgia Depression and southern regions of the Coast and Mountains, because of the presence of resident birds. On the Northern Mainland Coast, spring migration seems to occur in April. In the Southern Interior there is an increase in observations between January and April, which may reflect increased numbers due to spring migration, but a steep decline in records between April and May certainly reflects a movement of wrens from valley bottom localities to higher-elevation forests. In the Southern Interior Mountains, the first spring migrants arrive in March, but April probably sees the greatest movement. The small number of records for the northern regions of the province indicates that April is the month of spring arrival there. In the interior, the Winter Wren migrates out of regions north of about latitude 52°N in autumn, roughly the latitude of Williams Lake. It also moves away from high-elevation mountain slopes to winter in protected, low-elevation riparian habitats (e.g., Cannings et al. 1987). In the northern half of the province, southward migration begins by the end of July and is essentially complete by the end of August, although late migrants have been found in October in the Peace Lowland and in November near the Yukon border at Redfish Creek. In the Central Interior, the main departure occurs from August to October, although a few birds overwinter. In the Southern Interior Mountains, migrants leave mainly in September and October. Southern populations that breed near the timberline in the interior move to lower elevations by mid September. It is unknown whether or not some interior populations migrate to the coast for the winter. Autumn migration in coastal areas is difficult to discern. For example, although there seem to be higher numbers in winter than in summer in the Georgia Depression, the extent or timing of migration cannot be determined from our data. Along the coast and in the southern third of the interior, the Winter Wren occurs throughout the year; in the central interior, it has been recorded regularly from 16 April to 23 October; in the northern third of the interior, it has been recorded regularly from 23 April to 10 September, and as late as 18 November.

Breeding Nests Eggs Nest Success The Winter Wren breeds across much of the southern two-thirds of the province, including the Queen Charlotte Islands, Vancouver Island, other offshore islands, and the mainland coast, east across the southern portions of the interior to the Flathead River valley and north to the Skeena and Nechako river valleys. The northernmost breeding records are from Terrace, Smithers, Pine Pass, and Williston Lake. Nests with eggs or young have not been recorded north of latitude 56°N. Although we know of no confirmed breeding records, the Winter Wren probably breeds north to the Yukon border, as suggested by Godfrey (1986). The Winter Wren reaches its highest numbers in summer in the Georgia Depression and Coast and Mountains. An analysis of Breeding Bird Surveys for the period 196S to 1993 could not detect a net change in numbers on either coastal or interior routes. The Winter Wren has been reported breeding from near sea level to 2,100 m elevation. Most breeding sites were described as forest (78%; n = 171) or human-influenced habitats (19%). In forested habitats, coniferous forest was most frequently used (41%; n = 103), followed by mixed forest (22%) and human-made corridors through forest (18%). Both mature forests (26%; n = 76) and young forests (26%) were used, as were roadsides (20%) and backyards or farmyards (12%). The Winter Wren has been recorded breeding in British Columbia from 23 March to 12 September.

Nests:  Nests were found mainly in living and dead coniferous or deciduous trees (52%; n = 122) and banks and cliffs (24%). A few were found in buildings and sheds. Unusual nest sites included shrubs, a bridge, an abandoned automobile, and standing totem poles in an abandoned Indian village. Most nests were built in a cavity. Specific nest sites included natural cavities and those excavated by woodpeckers in living and dead trees or stumps (33%; n = 106), among the roots of overturned trees (26%), under an overhang in a soil bank or cliff or an overhang of a building (26%), attached to rafters, under loose bark or in bark crevices, suspended above ground in vertically oriented branches and sticks beneath clumps of shrubby vegetation, attached to a tree branch, in seabird burrows, and in a pair of snowshoes; 1 nest was found in a nest box.  The globular nest is usually well concealed and is composed of moss, twigs, grass, leaves, feathers, hair, plant fibres, rootlets, needles, shreds of rotten wood, and similar soft debris. The heights for 86 nests ranged from ground level to 7.0 m, with 61% between 0.8 and 1.8 m. Eggs: Dates for 61 clutches ranged from 23 March to 29 August, with 530 recorded between 20 April and 5 June. Sizes of 53 clutches ranged from 1 to 7 eggs (1E-7, 2E-3, 3E-3, 4E-7, 5E-17, 6E-13, 7E-3), with 57% having 5 or 6 eggs. The incubation period is variously stated to be 14 to 16 days (Bent 194S), 14 to 17 days (Harrison 1979), 11? to 16 days (Ehrlich et al. l9S8), and 14 to 20 days (Kluijver et al. 1940). Armstrong and Whitehouse (1977) state that incubation periods longer than 16 days are probably the result of delayed or irregular brooding. See further comments on incubation period in REMARKS. Nest Success: Of 7 nests found with eggs and followed to a known fate, 2 produced at least 1 fledgling. Young: Dates for 30 broods ranged from 6 April to 12 September, with 52% recorded between 13 May and 14 June. Brood size ranged from 1 to 7 young (1Y-2, 2Y-6, 3Y-3, 4Y-7, 5Y-9, 7Y-3), with 53% having 4 or 5 young. The nestling period is 15 to 20 days (Harrison 1979). Ehrlich et al. (1988) suggest that the Winter Wren may produce 2 broods a year, and some populations in British Columbia probably do so. Double-brooding can be established positively only where the nesting birds are banded or otherwise individually identifiable; however, records from the Queen Charlotte Islands suggest that at least part of that is land population nests twice in a summer. Records of 2 broods out of the nest on 29 May at Anthony Island and a pair nest building at Masset on 4 April establish the timing of the first broods, while a pair feeding nestlings at Rose Harbour on 26 August and a similar record for Hippa Island on 12 August suggest a second brood. There are similar data for Vancouver Island and southern portions of the interior. Brown-headed Cowbird Parasitism: Cowbird parasitism was not found in British Columbia in 83 nests recorded with eggs or young. Friedmann (1963), Friedmann et al. (1977), and Friedmann and Kiff (1985) do not list any occurrences for North America.

Remarks Two subspecies of Winter Wren occur in the province: T. t. pacificus west of the Rocky Mountains (Munro and Cowan 1947; American Ornithologists' Union 1957) and T. i. hiemalis in the Boreal Plains and possibly other boreal regions along the Yukon border. See Oberholser (1902,1920) for more details on subspecies. The Winter Wren is considered "exceptional and perhaps unique as a North American passerine which has successfully extended its range from North America into Asia, Europe, and North Africa" (Armstrong and Whitehouse 1977). These authors discuss variations in behaviour that lead to alterations in the apparent incubation period. They cite Kluijver et al. (1940) for the finding that in April and May incubation usually begins on the day the last egg is laid, whereas in June and July it often starts before the clutch is complete, thus leading to variation in incubation period. Some wrens may even begin incubation upon laying the first egg: 1 nest recorded in British Columbia was discovered on 23 May with a full clutch of 7 eggs. The hatching of the first nestling was noted on 26 May and proceeded with 1 egg hatching daily until 31 May. The nest was checked daily until 13 June, when all 7 young were still present.