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Mute Swans

The mute swan is a Eurasian species that was released by private individuals in New York prior to 1900. The species is now found from Massachusetts south to Virginia, as well as in Michigan, Oregon and several other states. The population trend for this species in the United States, as judged by the Breeding Bird Survey, has been steadily upward (Sauer et al. 2005). The recent trend in Maryland has been even more dramatic. In Maryland, 5 birds escaped in 1962, and the population is now approaching 4,000.

Despite their aesthetic appeal, mute swans pose a series of concerns (Maryland Department of Natural Resources 2003). They can be aggressive and sometimes threaten or attack people who get too close to their nest or young.

Mute swans consume enormous quantities of submerged aquatic vegetation. It is estimated that 4,000 mute swans could annually consume about 12% of the submerged aquatic vegetation in Chesapeake Bay. Submerged aquatic vegetation is critical to the health and well-being of many Bay organisms. Grazing of this resource by swans reduces the capacity of the remaining submerged aquatic vegetation beds to support wintering waterfowl and other fish and wildlife populations. Mute swans can reach 1 meter under water to graze vegetation, and they are present year-round unlike native tundra swans (Cygnus columbianus) which overwinter in Chesapeake Bay. Thus, the mute swans' impact on native submerged vegetation is extensive, both temporally and spatially.

Mute swans occupy and defend relatively large territories of wetland habitat during nesting, brood rearing and foraging, and thus compete with native birds for habitat. They displace native waterfowl and have been reported to attack, injure, or kill other wetland birds. In the early 1990s, 600-1,000 mute swans established a loafing area on oyster shell bars and beaches used as nesting sites by black skimmers (Rynchops niger) and least terns (Sterna antillarum). This resulted in abandonment of the site by these threatened waterbird species. In 2003, the Maryland Department of Natural Resources initiated a program of mute swan population control that included egg addling and culling adults. However, legal actions have repeatedly stopped current mute swan management programs.

Summary above taken from:

AVERY, M., AND E. TILLMAN. 2005. Alien birds in North America--challenges for wildlife managers. Proceedings of the Wildlife Damage Management Conference 11:82-89.

Literature Cited

Maryland Department of Natural Resources. 2003. Mute swans in Maryland: A statewide management plan. Wildlife and Heritage Service. On-line access at: http://www.dnr.state.md.us/wildlife/msfinaltoc.html

SAUER, J.R., J.E. HINES, AND J. FALLON. 2005. The North American breeding bird survey, results and analysis 1966 - 2004. Version 2005.2. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.