Beautiful but Controversial Birds
Story and Photographs by Larry J. Hindman
Mute swans have been cherished as symbols of purity and elegance for centuries. Native to Europe and Asia, they were transported to North America in the late nineteenth century by European immigrants. Some swans eventually escaped or were deliberately released into the wild.
Public opinion about mute swans is mixed. They are very large birds, measuring 56-62 inches in length. With little or no fear of humans, they are easily observed and provide opportunities for people to come in close contact with wildlife. Their vibrant orange bills with black knobs, white plumage and long, gracefully-held necks make them conspicuous. Their young, which have a dusky tinge and grayish bill, usually remain with their parents for about four months. Mute swans reside primarily in estuarine river habitats with smaller numbers on inland lakes and ponds.
Despite their aesthetic appeal, mute swans can cause problems. The mute swan is native to Europe and Asia, but is an exotic species in the United States. In Maryland, a feral population of about 4,000 mute swans has become established from the original escape of five captive swans in 1962. The largest number of mute swans occurs in Talbot, Queen Annes, and Dorchester counties. Population growth and range expansion of this species has increased the number of swan-related problems for people and native wildlife.
has increased the number of swan-related problems."
Citizens frequently complain that mute swans reduce the availability of submerged aquatic vegetation, or SAV, to native wildlife, reducing recreational crabbing and fishing opportunities. Presently, we estimate that Maryland's mute swan population consumes about nine million pounds of SAV annually. Concentrations of mute swans have over-grazed bay grasses, eliminating habitats for crabs, fish, and other wetland dependent species.
In the early 1990s, a large molting flock of mute swans caused a colony of least terns and black skimmers, both state-threatened species, to abandon their nesting site on Barren Island in Dorchester County by trampling nests containing eggs and chicks. This was the only skimmer nesting colony in the Maryland portion of Chesapeake Bay. These swans also displaced nesting Forster's and common terns, declining species in Maryland. In other areas of the state, mute swans have also been documented killing mallard ducklings and Canada goose goslings.
A major concern is the effect of interspecific competition between mute and tundra swans. Mute swans have been observed exhibiting aggression toward tundra swans, driving them from protected coves and feeding areas, important habitats for native tundra swans. Since the mid-1970s, Maryland's wintering tundra swan population has declined by about 30%. However, research is needed to determine if this decline is related to an increase in competition between native tundra swans and exotic mute swans.
In the absence of active control measures, it is expected that the number of feral mute swans in Maryland will continue to increase. Eventually, this species could occur in larger numbers throughout the Chesapeake Bay regions and cause additional ecological harm and problems for humans.
Since the mid-1990s, the Maryland Department of Natural Resources (DNR) and some Federal agencies within Maryland have controlled mute swans to prevent their establishment on lands that they manage. Control has included preventing eggs from hatching, live capture and removal of adult swans and humane euthanasia of adult swans. The DNR authorizes landowners to control swans that cause either nuisance or property damage problems. These mute swan control activities have also been combined with efforts to increase public aware ness of the problems caused by mute swans. In general, control has been supported by the public. However, animal rights activists object to lethal control methods.
In late 1998, Maryland's Governor, Parris Glendening, appointed a committee to develop management recommendations for the mute swan. This process is expected to result in recommendations that will include a combination of nonlethal and lethal control methods aimed at reducing the mute swan population to a level that is compatible with native wildlife and will reduce conflicts with humans.
Note: Larry J. Hindman is the Waterfowl Project Manager for the Maryland Department of Natural Resources, Wildlife and Heritage Division.
Waterfowl Project Manager's Page
Wildlife and Heritage Home Page
DNR Home Page