Over the past century, ornithologists throughout the Appalachian region have recorded a gradual but steady population decline of a small bird called the Appalachian Bewick's Wren (Thryomanes bewickii). Historically fairly common around towns and farms of central Appalachia, today the Appalachian Bewick's Wren is a rare sight. Only twenty pairs have been noted during this decade in Maryland, Virginia, and West Virginia combined, and biologists are at a loss to determine exactly why this bird has been pushed to the edge of extinction.
Smaller than the Carolina Wren, the Appalachian Bewick's Wren is approximately five inches long. Adults have medium brown upperparts with a white throat and breast. The white-fringed tail and the prominent white stripe over the eye readily distinguish the Bewick's Wren from other wrens. Also distinctive of this species is its habit of constantly twitching its tail from side to side. Its song, resembling a Song Sparrow's, is high pitched and ends in a trill.
The Appalachian Bewick's Wren ranges over much of the central and southern United States. Biologists recognize several distinct populations of the species according to geographic locations. Some populations west of the Mississippi River have remained relatively stable. However, those east of the Mississippi are experiencing dramatic declines, and in some states, this bird has totally disappeared. The Appalachian population of the Bewick's Wren historically ranged from southwestern Pennsylvania, Ohio, and Kentucky south to Georgia and Alabama. Conservationists are most concerned about this population.
The Appalachian Bewick's Wren may be found in a variety of habitats, including thickets, open woodlands and farmlands, and scrubby areas, and is often found near streams. In the East it lives at elevations up to 4000 feet. Like other wrens, the Bewick's feeds primarily on insects. Preferring to nest in cavities, the wren builds sturdy nests of twigs, leaves, feathers, and other materials. The female lays between five and eight eggs, which she incubates for two weeks. The young are ready to fledge (to leave the nest) within two weeks after hatching. The Appalachian Bewick's Wren winters from the southern limits of its summer range south to the Gulf of Mexico. Little is known about the bird in its winter range.
Because the Appalachian Bewick's Wren has been undergoing a gradual population decline over the past four to five decades, scientists were slow to recognize the severity of the trend. The Appalachian Bewick's Wren has now all but vanished from its historic range in the Appalachians. Surveys conducted in Pennsylvania through Alabama have failed to produce more than ten sightings over the last three years. In 1983, the last pair reported in Maryland was sighted at Dan's Rock in Allegany County. Today, little time is left to protect the population from extinction.
No bird more deserves protection ... than the Bewick's Wren. He does not need encouragement, for he comes of his own accord and installs himself as a member of the community wherever it suits his taste. He is found about the cowshed and barn; he investigates the pigsty; then explores the garden fence, and finally mounts to the roof and pours forth one of the sweetest songs that ever was heard.
---Robert Ridgeway, 1889
This passage from the notebook of the 19th century naturalist Robert Ridgeway not only demonstrates how common the Appalachian Bewick's Wren was during the last century, but also expresses the bird's tendency to live near people. Repeatedly, birdwatchers and ornithologists have remarked on the many peculiar choices of the wren for nesting, including straw hats, coat pockets, fish nets, mail boxes, and tin cans. This remarkable adaptability of the Appalachian Bewick's Wren makes its population decline all the more mysterious to biologists.
In many cases, when an animal suffers a decrease in population, it is due to loss of habitat. In the case of the Appalachian Bewick's Wren, however, biologists cannot draw that conclusion. Since the wren is so adaptable and ample habitat remains for the bird, the reasons for its decline may be less obvious. To this day, those reasons remain unclear.
Perhaps the most common theory for the decline of the Appalachian Bewick's Wren is competition with other birds, primarily the House Wren. This smaller but more aggressive relative has been expanding its range in the East to areas once dominated by the Bewick's. Over the decades, forest fragmentation has increased the amount of edge and scrub habitat, apparently facilitating the House Wren's expansion. As early as the 1930s, naturalists noted fighting between the two species, followed by displacement of the Bewick's Wren into less desirable habitat. However, the House Wren's expansion, enabled by land-use changes that should also have favored the Bewick's Wren, may be simply coincidental to its decline.
Other species with possible contributory roles in driving the Appalachian Bewick's Wren from its optimal habitat include the Song Sparrow, the Carolina Wren, and two introduced species: the European Starling and the House Sparrow. These four are all found within the Bewick's population range and often favor similar nesting sites.
Other theories for the decline of the Appalachian Bewick's Wren suggest that the population may have been struck with an epidemic or may have suffered from severe winter weather over consecutive years. One theory, yet to be investigated, suggests that the decline is due to loss of winter habitat or to other events occurring in the wren's winter range.
Biologists may never find conclusive evidence that one or more of the factors in these theories contributed to the precipitous decline of the Appalachian Bewick's Wren, primarily because there are so few birds from which to glean information. More clues are needed before conservation agencies will be able to provide meaningful help in recovery of species.
The decline of the Bewick's Wren in Appalachia has been a major concern of the Wildlife and Heritage Division of the Maryland Department of Natural Resources, which monitors the status of rare plant and animal species in the State. Since 1986, the Appalachian Bewick's Wren has been classified as Endangered under regulations of the Maryland Endangered Species Act of 1971. This classification provides important status for the species, protecting the wren from many human-caused forms of disturbances. Unfortunately, with no breeding Appalachian Bewick's Wrens known to be left in the State, this protection may have come too late. Any Bewick's Wrens discovered in Maryland will become a high priority for protection by the Service.
Maryland Department of Natural Resources
Wildlife and Heritage Division
Tawes State Office Building, E-1
Annapolis, MD 21401
Written by Johanna Thomas with the assistance of D. Daniel Boone, Rodney L. Bartgis, and Lynn Davidson of the Wildlife and Heritage Division, Maryland Department of Natural Resources. Bewick's Wren illustration by Michael O'Brien.
580 Taylor Ave, Annapolis MD 21401