Introduced Species Summary Project
Mute Swan (Cygnus olor)

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Common Name: Mute Swan (Domestic Swan, Wild Swan, Tame Swan)

Scientific Name:  Cygnus olor


Phylum:  Chordata
Subphylum:  Vertebrata
Class:  Aves
Order:  Anseriformes
Family:  Anatidae

Identification:  With their distinctive white plumage, mute swans are one of the largest waterfowl in North America weighing up to 13kg.   Adults grow to 1.50m in length with wingspans up to 2.4m.  Their orange beak with the black basal knob and terminal nail distinguishes mute swans from all other species of swans.  Mute swans have webbed feet that range in color from black to grey-pink.  While swimming, the birds hold their necks in a characteristic “S” shaped curve.  Juvenile mute swans, or cygnets, have grey or white colored down.  Their grey or tan beaks lack the characteristic basal knob of the adults.  As their name suggests, mute swans are generally silent.  They lack the loud discernable calls often characteristic of other bird species.  The few sounds made by the mute swans can only be heard from a short distance and include puppy-like barking noises, hissing sounds and high-pitched whistles.  On the contrary, the bird’s wing beating behavior during flight can be heard over very long distances.

Original Distribution:  The original breeding grounds of the mute swan are in the British Isles, northern Europe and north central Asia.  Since they are a status symbol in European cultures, mute swans have been domesticated in Western Europe since the 12th century.  In their native land, the birds migrate to their wintering grounds in North Africa, the Near East, northwest India and Korea.

The distribution of Mute Swans in the United States

Current Distribution:  Today in the United States mute swans can be found in lakes, ponds and estuaries as far west as Washington State.  But the majority of the bird’s distribution is limited to the freshwater and estuarine areas of the Northeastern and Midwestern United States.  There are substantial populations in the Chesapeake Bay, the Long Island Sound and the Great Lakes.  While the birds migrate in their native distributions, there are no mass migration events in the United States.

Site and Date of Introduction:  Mute swans were introduced to the northeastern United States in the late 19th century from Western Europe.  The majority of the introductions occurred on Long Island and in the Hudson Valley area of New York State.  Other areas of the world where mute swans have successfully invaded include Canada, Australia and Tasmania.

Modes of Introduction:  Mute swans were intentionally introduced to the United States.  Europeans transported the birds to New England for display as decorative waterfowl in zoos, parks, avicultural collections and private estates.  Mute swans were favored in New England by breeders of waterfowl for their beauty and grace.  Between the years of 1910 and 1912, over 500 mute swans were brought to the United States from Europe.  While most of the captive mute swans in New England had their flight feathers clipped, a small number of birds escaped from captivity.  The first birds to escape in the United States are believed to have done so in the Hudson Valley in 1910 and Long Island, New York in 1912.  A few other birds are thought to have been intentionally introduced into the wild throughout New England.  Feral populations were then quickly established, spreading as far south as New Jersey by the 1930’s.  By the late 1960’s, populations of feral mute swans were recorded in Pennsylvania, Maryland, Delaware, and Virginia, thus severely affecting the Chesapeake Bay watershed.   An escaped population of only five birds in 1962 from a captive population in Maryland has resulted in a population of feral mute swans of over 4,000 individuals.  Established populations in the Great Lakes and the Long Island Sound are also causing extensive damage to the freshwater and brackish ecosystems.

Reasons Why it has Become Established: The birds have thrived in the northeastern United States because of the similar climatic conditions to their native land and presence of freshwater habitats.  Due to their size, overly aggressive behavior and hostile territoriality mute swans out-compete many native birds for food and nesting sites and relatively low predation rates.  Owing to this assertive behavior, mute swans are also able to establish populations in new areas fairly quickly.  Mute swans have been protected by state legislation because they fall under laws concerning waterfowl and wetlands protection.   Since 1980, the mute swan population in the Eastern United States has grown by 10-30% per year.

Ecological Role:  Mute swans are herbivorous aquatic foragers. An individual adult swan consumes 3-4kg of submerged aquatic vegetation (SAV) per day.  The remainder of their diet includes a small proportion of terrestrial plants, algae, insects, fish and frogs.  In their native lands, mute swan feeding habits aid other waterfowl’s foraging as they stir up vegetation deep in the water that smaller waterfowl, such as ducks, cannot reach.  If left unprotected, medium-sized predators, such as mink and raccoons, will take eggs and cygnets.  Adults are not usually preyed upon unless they are injured or sick. 

Benefits:  For centuries mute swans have an aesthetic appeal due to their size, color and gracefulness.  In some European cultures they are a status symbol and have been domesticated.  The swans bring enjoyment to many people because they are conspicuous bird that may be fed, photographed and observed for their many interesting behaviors.  The swans display little fear towards humans, allowing close viewing of wild animals.  The swans are sold for display in residential lakes.  Mute swans have been used as biological control of filamentous algae in small ponds and to reduce nuisance problems caused by resident Canadian geese.  A pair of mute swans can be purchased for $500, indicating a high economic value.

Threats:  Mute Swans have been devastating to freshwater SAV communities in the United States.  While feeding, the birds uproot and dislodge three times the amount of SAV they ingest.  Therefore an estimated 13kg of SAV per day are removed by a single mute swan.  When populations of mute swans can reach numbers in the thousands, the result is a substantial loss of SAV.  Grazing by mute swans has been so severe that they have caused rapid local extinction of a number of plant species.  SAV is vital to the freshwater and brackish ecosystems because it provides food, shelter and breeding areas for economically and ecologically important species of fish, invertebrates and shellfish.  SAV also provides food and nesting sites for resident and migratory waterfowl.  This vegetation also has the ecosystem function of improving water quality through filtering out sediments and pollutants from runoff. 

Mute swans out-compete native waterfowl for habitat and food.  Studies have shown that mute swans graze on the same SAV species as native waterfowl.  Since mute swans are non-migratory, they reduce the available habitat for native breeding and wintering birds year round.  Due to their aggressive territorial behavior, mute swans have caused the nest abandonment of least terns and black skimmers, both threatened species.  They have also been known to kill adult and juveniles geese, ducks and a number of other wetland birds.  Mute swans further reduce the viability of native waterfowl by hybridizing with trumpeter swans and tundra swans.  Mute swans also pose a threat to humans.  The birds have known to attack and critically injure children and pets.  They are also nuisance problem causing serious property damage which results in economic losses. 

Control Level Diagnosis:  Highest priority.  Mute swans are significantly affecting the structure and functioning of ecosystems and are reducing the biodiversity of wetlands.

Control Method:   Management of mute swan populations has been a major concern since the 1970’s.  Currently the population of mute swans on the Atlantic coast of the United States is over 14,000 birds.  An objective of the Atlantic Flyway Council is to reduce this swan population to less than 3,000 birds by 2013.  In order to meet such a goal, a vast amount of birds will need to be removed through lethal and non-lethal methods.  Egg addling and nest destruction, while more acceptable to the public, is not as effective as reducing adult survival through hunting or capture and humane euthanasia.  Many management programs have been met with protest from animal rights groups.  As a result, it is of importance to survey public attitude towards different methods of control and to increase public awareness of the status and threat of mute swans in their area. As always, communication between government, managers and scientists should to be encouraged in order to establish effective legislation.  In addition to relieving any laws that protect wild mute swan populations, legislation needs to be implemented concerning the control of captive mute swan populations. 
Atlantic Flyaway Council: Atlantic Flyaway Mute Swan Management Plan 2003-2013.  Prepared by the Snow Goose, Brant and Swan Committee.  Jul 2003.

Day, L.  The City Naturalist – Mute Swan. NY Site: West Side.  79th Street Boat Basin Flora and Fuana Society. 1996.

Hindman, L. J. Mute Swan: Beautiful but Controversial Birds.

Ivory, A. 2002. Cygnus olor (mute swan), Animal Diversity Web.

Mute Swan (Cygnus olor) in the Chesapeake Bay: A Draft Bay-Wide Management Plan.  Prepared by: The Chesapeake Bay Mute Swan Working Group. Chaired by: Julie A. Thompson. United States Fish and Wildlife Service, Chesapeake Bay Field Office. Nov 2003.

O’Connell, K. A.  Mute Swans Spark Loud Debate in Chesapeake Bay. 05 Jun 2003. National Geographic News.

Petrie, S. A. and C. M. Francis. Rapid Increase in the Great Lakes Population of Mute Swans.

Population status, nutrient reserve dynamics and dietary intake of Mute Swans on the lower Great Lakes.  The Long Point Waterfowl and Wetlands Research Fund. Bird Studies: Canada.

Swans at Berwick: Mute Swans.

Map taken from: Mute Swan Cygnus olor: Map of Winter Distribution from CBC.

Author and Photographs: Meredith Walsh
Last Edited: November 21, 2004

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