Final Report (~8.3 mb pdf)
Species Specific Session Abstract
Status and Management of Mute Swans in Maryland
Larry Hindman
Maryland Department of Natural Resources
Since the escape of five mute swans (Cygnus olor) from captivity in 1962, the feral mute swan population in the Maryland portion of Chesapeake Bay has increased to over 4,000 birds. This increase represents an annual growth rate of about 23% between 1986 and 1999 and 12% between 1993 and 1999. At these growth rates, the population could reach 13,500 (at 12%) to 38,500 (at 23%) by 2010. Although valued for their aesthetic beauty, some mute swan pairs have become a nuisance, preventing people from using their riparian waters where swans vigorously defend their nests and young during the breeding season. Since 1986, conflicts between mute swans and native wildlife have increased, resulting in the displacement of colonial waterbirds and native waterfowl from nesting areas. Furthermore, mute swan grazing on SAV (submerged aquatic vegetation) has reduced the carrying capacity of wetlands for native waterfowl and other fish and wildlife. Although the impacts on SAV are not well quantified, maintaining a large mute swan population is inconsistent with the 2000 Chesapeake Bay Agreement objective of restoring 114,000 acres of SAV. This overabundant, invasive population of mute swans poses a challenge to wildlife managers. Population modeling suggests that it would be necessary to reduce recruitment by 80% merely to stabilize the population. A combination of reducing both recruitment and adult annual survival is the most effective means of either stabilizing or reducing the population to a level that is compatible with the Bay's living resources.
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