Bewick's Wren

BEWICK’S WREN

Photo Credit: Bill Horn
http://www.birdsofoklahoma.net/index.html

SCIENTIFIC NAME: Thryomanes bewickii (Audubon)

OTHER NAMES: House Wren (Kennedy and White 1997).

DESCRIPTION: A rather large (13 cm [5.1 in.]), long-tailed drab wren. Sexes identical in plumage color and pattern. Back and crown coloration of eastern populations flat brown, lacking rich rufous tones of Carolina wren. Underside grades from fairly bright white on throat to dull gray on undertail. Lower breast and belly lack rufous coloration of Carolina wren. A white eyebrow stripe separates crown and cheek. Have bold black and white markings along margin of tail that separates them from all other wren species. Male’s song usually composed of five phrases and sounds like, seee-teu-whee-teu-eeee (Kennedy and White 1997). Approximately 19 extant and one extinct subspecies. Although distinctness questionable, eastern populations divided into two subspecies (AOU 1957, Kennedy and White 1997), the nominate race, T. b. bewickii, winters in Alabama, and the Appalachian race, T. b. altus, once bred in Alabama (Imhof 1976). Eastern subspecies browner than western subspecies.

DISTRIBUTION: Were absent from Midwest and southern Appalachian region at time of European settlement. With fragmentation of forests of Midwest and southern Appalachian regions, suitable habitat was created and they moved north and east. Between early nineteenth and early twentieth centuries, colonized a large area of eastern North America from Illinois to New York to Georgia. Established breeding populations in Georgia by 1854, Tennessee by 1886 (Kennedy and White 1997), and presumably colonized Alabama during same period, but no records exist. Howell (1928) reported them as a fairly common summer resident in the northern half of the state but “nowhere so abundant as the Carolina wren.” In winter he reported them “found in moderate numbers all over the State.” Howell (1928) makes no mention of changes in abundance. Declines in abundance and a retraction of the breeding distribution began in the northern and eastern portions in the 1920s (Kennedy and White 1997) and were noted in Alabama by 1960 (Imhof 1976). Breeding bird survey data show declines from 49 percent of eastern U.S. routes in 1966 to 12 percent of routes in 1979 (Robbins et al. 1989) to virtually no routes in 1990. By the turn of the millennium, had disappeared as a breeder from all but a few localities in the Midwest or southern Appalachians and is still declining (Kennedy and White 1997). Although probably bred in Alabama in 1975 and 1976 at various locations (Reid 1976), the last confirmed breeding record was in 1974 at Newburg, Franklin County (G. Jackson, pers. comm.). Individuals still occasionally observed in Alabama in migration and during winter (Jackson 2001a).

HABITAT: Open habitat with clumps of vegetation. Did not occur in deciduous forest. In the east, including Alabama, were birds of farmyards and rural dwellings. Also found in windrows or slash piles created from clear-cutting operations (Robinson 1989). Were famous for nesting in buckets hanging in sheds, abandoned cars, and even in the pockets of clothes on clothes lines. Most nests in Alabama were associated with human dwellings. Avoided wet lowlands, preferring uplands, especially hilltops (Howell 1928).

LIFE HISTORY AND ECOLOGY: Eastern populations at least partly migratory with birds from the northern portion of distribution moving south, but there are few band recoveries and no detailed information on migratory movements (Kennedy and White 1997). Migratory males sing upon arrival on breeding area in spring. Resident males may start singing as early as January. Males use song to defend territories that usually are established around human structures in Alabama. Typically, monogamous pairs are formed as females choose territorial males, but occasionally a male will pair with more than one female (Kennedy and White 1997). Both sexes build a cup nest placed in a cavity, or on a shelf. Female lays three to eight white eggs (average [mean] = 5.6) that are finely spotted with reddish brown, and incubates alone (14 to 16 days) with male providing her with some food. Nestling period is 14 to 16 days and young remain on natal territories for about five weeks. Both parents feed young through the fledgling stage. Some pairs produce two broods per season (Kennedy and White 1997). Diet includes arthropods such as bugs, beetles, bees and wasps, butterfly and moth larvae and adults, grasshoppers and crickets, and spiders, as well as plant material such as fruit pulp and seeds. Predators include snakes and birds of prey (Kennedy and White 1997). After breeding, males stop singing and defending territories. Migratory individuals move south. Whether birds migrate or not, males and females separate and establish individual home ranges during winter (Kennedy and White 1997).

BASIS FOR STATUS CLASSIFICATION: Have undergone a precipitous decline to virtual extinction in the twentieth century. In Alabama, may now be extirpated as a breeding bird (Jackson 2001a). With the possible exception of the cerulean warbler, no other bird in Alabama in recent history has declined as rapidly to such a low end point. Over about four decades the species went from being widespread and fairly common to virtually extinct. Habitat modification by humans is unlikely to have directly caused the decline because the rural setting favored by Bewick’s wrens remains widespread across the former breeding distribution, including northern Alabama. The current, most widely suggested, explanation for the decline is competition with house wrens. House wrens are known to destroy the eggs and nests of other birds and they seem particularly aggressive toward Bewick’s wrens (Imhof 1976, Kennedy and White 1997). The expansion of the distribution of the house wren coincided fairly closely with the decline of Bewick’s wrens (Kennedy and White 1997). However, house wrens and Bewick’s wren’s had coexisted for decades in some portions of the Midwest, and Bewick’s wrens disappeared from many regions before the appearance of house wrens (Wilcove 1990). Further, house wrens have never been considered a regularly breeding species in Alabama (Howell 1928, Imhof 1976). Perhaps competition with the much more common Carolina wren has contributed to the decline in the Southeast. It has also been suggested that the rapid decline was caused by an epizootic (Wilcove 1990), but that hypothesis is now untestable. The presence of occasional wintering birds in southern Alabama indicates that a few individuals still occur in the state and that it deserves protection.

Author: Geoffrey E. Hill


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