Thryomanes bewickii

A medium-sized (5 ¼ inches) wren, Bewick’s Wren is most easily identified by its plain brown back, pale breast, long tail (often held up at an angle), long curved bill, and conspicuous white eye-stripes. This species may be distinguished from the similar House Wren (Troglodytes aedon) by that species’ small size and fainter eye-ring and from the Carolina Wren (Thryothorus ludovicianus) by that species’ larger size and warmer-toned plumage. Male and female Bewick’s Wrens are similar to one another in all seasons. Bewick’s Wren primarily occurs in western North America from British Columbia south to central Mexico and east to the central Great Plains. Although this species was formerly widespread in the eastern United States as far north and east as the Mid-Atlantic region, its range in those areas is greatly reduced today compared to a century ago, with isolated pockets persisting in the Ohio River valley and the southern Appalachian Mountains. In this species’ core range, most birds are non-migratory, although some birds at the northern or southern extremities of this range migrate short distances south in winter. Bewick’s Wrens inhabit open areas with thick ground cover, such as bushy fields, thickets, and dry scrubland. Eastern populations are heavily dependent on land cleared for agriculture, and much of this species’ decline in those areas is thought to have been caused by the return of woodland habitats to its favored abandoned agricultural fields. Bewick’s Wrens primarily eat small insects, but may also eat small quantities of seeds and berries during the winter when insects are scarce. In appropriate habitat, Bewick’s Wrens may be seen foraging for food on the ground or in the branches of bushes and shrubs. Birdwatchers may also listen for this species’ song, a series of buzzing notes recalling that of the Song Sparrow (Melospiza melodia). Bewick’s Wrens are most active during the day.

Threat Status: Least concern

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) BREEDING: historically, mainly from southwestern British Columbia, western and central Washington, western and southern Oregon, northern California, west-central and southern Nevada, southern Utah, southwestern Wyoming, central Colorado, Kansas, southeastern Nebraska, southern Iowa, extreme southern Great Lakes region, and southeastern New York, south to southern Baja California, northern Sonora, in Mexican highlands to central Oaxaca, western Puebla, and west-central Veracruz, and to southern Tamaulipas, central Texas, northern Arkansas, northern portions of the Gulf states (except Louisiana), and central South Carolina (AOU 1983). Formerly occurred on San Clemente Island (California) and Isla Guadalupe (Mexico). Species has nearly disappeared from all of the range east of the Mississippi River (Kennedy and White 1997). The greatest numbers are now, and probably always have been found, in the southwestern U.S. The highest encounter rates from 1976 to 1985 were found in central and southern Texas, central and southern Arizona, and southern and northcentral California. Highest average birds per BBS routes (1982-1991) were located in Arizona (9.67), Texas (5.24), California (4.25), New Mexico (3.37), and Oklahoma (2.57). A small population concentration also exists in western Washington. Eastern states, in contrast, average 0.05 birds per route. NON-BREEDING: northern limits of breeding range (west of the Rockies), Kansas, Missouri, lower Ohio Valley, Tennessee, and North Carolina south to limits of breeding range in Mexico, the Gulf coast, and central Florida (AOU 1983). The population east of the Mississippi has nearly disappeared. Subspecies ALTUS: historically, Appalachian region from southern Ontario, central Ohio, and cental Pennsylvania south to central Alabama, central Georgia, and central South Carolina, wintering south to the Gulf coast and central Florida (AOU 1957); now very local and rare in this range.

Length: 13 cm

Weight: 10 grams

Systems

• Terrestrial

Comments: BREEDING: Uses brushy areas, thickets and scrub in open country, open and riparian woodland, and chaparral. More commonly in arid regions but locally also in humid areas (subtropical and temperate zones) including country towns and farms (AOU 1983). In southwestern North America, primary habitats include chaparral, brushy slopes, pinyon-juniper, live-oak, and mesquite associations. In southwestern Wyoming, preferred woodlands with a combination of pinyon pine and high overstory juniper cover (Pavlacky and Anderson 2001). Along the northern Pacific coast, occurrences are in rough country, clearcut forests, open second-growth, and in the vicinity of human habitations (Bent 1948). In eastern North America, generally occurs at higher elevations of the Appalachians in farmyards, brushy places, openings and edges of woodlands, and overgrown fields. Typically nests in natural tree cavities or among crannies formed by exposed roots. May use small cavities in human-made objects including fence posts, buildings, or bird houses.

Its habitat during the period of peak abundance and expansion in 1800s and early 1900s was different from that of the current population. For example, in North Carolina during the early 1900s, wrens commonly occurred in towns and farmyards at all elevations of the mountains (Pearson et al. 1942, Potter et al. 1980). Most of the North Carolina records since 1950 have been in forest openings, pastures with fences and brushpiles that are away from human habitation and above 4.000 feet.

NON-BREEDING: eastern birds abandon montane habitats, moving into weedy open country, especially around old farm buildings, brushpiles, and fencerows, at lower elevations.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Northern breeding populations are partially migratory in the east, move south for winter. Elevational migrations occur in some areas. In the western half of the United States, the Bewick's wren is essentially non-migratory. However, the populations found in the Appalachians and in the Midwest are migratory, and travel in early spring, often arriving in March (Stupka 1963). The birds remains on the breeding grounds until October or November. Those that nest in the Appalachians and Midwest winter farther south, mainly from Kentucky and Missouri southward to the Gulf Coast, but they are very rare in Florida.

Comments: Insects comprise about 97% of the diet (beetles, leaf bugs, stink bugs, boll weevils, grasshoppers, etc). Also eats spiders and other small animal food. Forages on the ground, among foliage and limbs of trees and bushes, on logpiles, or around old buildings. Most of its foraging occurs within ten feet of the ground.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: Numerous occurrences, especially in the southwestern U.S.

10,000 to >1,000,000 individuals

Comments: Common in southwestern U.S. Average number of birds per Breeding Bird Survey route in southwestern states was as high as 9.7 in Arizona. On the other hand, the Appalachian population is nearly extirpated, and all BBS routes had much fewer than 1.0 bird per route.

Maximum longevity: 8 years (wild)

Lay eggs from April into June, with from four to nine (usually five to seven) eggs per clutch. Generally, two or three broods are raised per year (Potter et al. 1980). The female incubates and the chicks hatch after approximately 14 days. Juveniles fledge approximately 14 days after hatching. Both parents feed until young are 28 days old (Bent 1948, Harrison 1978).

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 10 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 11
Specimens with Barcodes: 17
Species With Barcodes: 1

Year Assessed

Assessor/s

Reviewer/s

Contributor/s

Justification

History

• 2008
  Least Concern
• 2004
  Least Concern

Canada

Rounded National Status Rank: N4B - Apparently Secure

United States

Rounded National Status Rank: N5B - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread and common in many areas in western North America; major declines, probably related to habitat loss and habitat succession, have occurred east of the Mississippi River.

Global Short Term Trend: Decline of 10-30%

Comments: North American Breeding Bird Survey (BBS) data reveal that the species has been declining in parts of the U.S. for some time. Populations in the central and eastern parts of the range are smaller than they were in the past, and recent declines have been evident in California and Washington. Eight states, Wisconsin, Michigan, Ohio, Pennsylvania, West Virginia, Virginia, North Carolina, and South Carolina, reported declines between the 1950s and the 1980s from rare or local breeders (or "common" in the case of North Carolina) to near or certain extirpation. Tennessee also reported a precipitous decline over the same period, but still has a few occurrences in the mid-state region. During the period of 1965 to 1979 severe declines occurred in Eastern and Central regions while the West was stable. Declines are noted especially in Kentucky, Missouri, Oklahoma, Tennessee, Texas, and no increases were detected in any states or strata. In the 1980's the decline in the central states subsided, while the population in the Eastern states continued to decline to the point that BBS data was no longer reliable for use in trend analysis (Peterjohn, pers. comm.). From 1982 to 1991 the Central region population showed an overall increase. Texas and the Osage Plain stratum showed increasing populations (plus 4 percent per year in Texas, plus 8 percent per year in the Osage Plain). These were the only positive trends registered in any state, stratum, or region during this decade (considering only those with adequate sample size and abundance for trend analysis). The West, however, showed a decline of more than 5 percent per year. Both California and Washington registered declines of more than 6 percent. Declines occurred in areas (Pinyon-Juniper, California Foothills, and Southern Pacific Rim strata) which have had sizable populations of this wren. This decline apparently has not been discussed in the literature yet. Maryland's Natural Heritage Program (1986) prepared "A Petition to List the Appalachian Population of Bewick's Wren as Endangered" in 1986. This account details state by state trends within the range of the Appalachian race of this species. The report concludes that whereas the species was considered common to abundant in most of twelve eastern states from southern Ontario to Alabama and Georgia prior to World War II, by the early 1980s, it was only documented as a breeding bird in Maryland, Virginia, and West Virginia. Fewer than 20 pairs were documented in the period of 1981-1985. The report suggested that the decline was "so severe that it may already be beyond the point of recovery for the population" (Maryland NHP 1986, p 1).

Degree of Threat: BC

Comments: Threats are poorly defined, but eastern populations are clearly threatened, and possibly western populations as well. Declines may be due to interspecific competition, habitat changes, inclement weather, and predators. Interspecific competition has been strongly linked to the decline. Starlings (STURNUS VULGARIS), house sparrows (PASSER DOMESTICUS), house wrens (TROGLODYTES AEDON), Carolina Wrens (THRYOTHORUS LUDOVICIANUS), and Song Sparrows (MELOSPIZA MELODIA) are likely competitors although it is difficult to attribute decline entirely to competition with any one species (Byrd and Johnston 1991, Ehrlich et al. 1992, LeGrand 1990, Simpson 1978). In Tennessee, for example, the decline began prior to the arrival of House Wrens (Hamel 1992). It is also difficult to ascertain what limiting resources are involved in the competitive exclusion of this species. Nest sites (cavities and crannies in tree trunks, base of trees and shrubs, or in buildings), for example, are not likely to be in short supply. Insects, the wren's food source, are seldom a limiting factor in the breeding season in the eastern U. S. (LeGrand and Hall, unpubl. data). Byrd and Johnston (1991) suggest that modern suburbanization and forest regrowth may be the most likely reason for the population decline. The San Clemente and Guadalupe Island subspecies, for example, are extinct due to habitat destruction caused by introduced livestock. Additional factors in the decline may be related to a series of harsh winters in 1957 and during the late 1970's (Mengel 1965, Robbins et al 1986, Peterjohn 1989). Bent (1948) noted also a few instances of brown-headed cowbird (MOLOTHRUS ATER) and bronzed cowbird (MOLOTHRUS AENEUS) parasitization. Predators include hawks, owls, and snakes. Pesticides are not known to be a problem, but it is unclear whether or not this has ever been directly investigated. Threats in the far West, where the species may also be declining, have not been analyzed.

Restoration Potential: Until the causes of decline are found, recovery is unlikely. Release into formerly occupied habitat is not likely to succeed until reasons for the decline are found and the possibility of controlling threats is explored.

Preserve Selection and Design Considerations: Land protection is not a viable alternative for protection. Wrens nest in human-altered habitats such as farmyards or openings in forests. Though territories are small, perhaps five acres, the decline does not appear to be based on loss of habitat. Protection of land would not provide protection from competing species or severe winters (LeGrand and Hall, unpubl. data).

Management Requirements: Management needs are poorly defined because of the lack of understanding of the decline in the East. However, the following are a few considerations based on current knowledge: 1) Removal of competitors in the vicinity of nests would likely benefit if competitors are the limiting factor. However, removal may be impractical because of high abundance of introduced species such as house sparrows and starlings. Native competitors are protected species. The procedure would be costly and likely unproductive. 2) Habitat management might be necessary in areas where farmland is converting to forest. Prescribed burning or other techniques that maintain early successional stages (open scrub woodland) may be beneficial in the eastern U.S. 3) Construction of nest boxes may be beneficial if nest sites are a limiting factor. See Mitchell (1988) for construction specification and placement of nest boxes. Nest boxes are inexpensive and effectiveness needs to be evaluated. Boxes placed in high elevation pastures and other semi-open places with brushpiles, fence rows, and shrubbery might attract wrens. However, they would likely attract other species as well.

Management Research Needs: The primary research need is to determine the reason for the decline in the East, and possibly, on the Pacific Coast. This will be difficult to accomplish in much of the eastern range because of rarity. In those Eastern states where small numbers still breed, research is needed to determine threats, and to experiment with management practices, such as nest boxes or competitor exclusion. Also needed are: basic information on ecology, including food resources and relationship to competitors, predators, and nest parasites.

Global Protection: Unknown whether any occurrences are appropriately protected and managed

Needs: Populations east of the Mississippi require intervention to prevent complete extirpation. It would be appropriate and helpful to list species as Threatened or Endangered in all states east of the Mississippi with present or recent breeding populations, and to proceed with federal listing for the Appalachian population. Initiate protection measures should western populations continue to decline.

Stewardship Overview: On the verge of extirpation in the eastern U.S., it has no remaining population strongholds in this region. In the Central states, it appears to have a stable or increasing population in its center of greatest abundance in Texas. In the West, it appears to have begun declining fairly rapidly along the Pacific Coast, especially from northern California northward. It would be useful to determine the extent of the current population in the eastern states and if there are yet any population centers of viable size. Suggested actions include a public call for information about sightings in the East, with follow-up by researchers. An experimental nest box program should be evaluated.