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
Classification:
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.
References:
Atlantic Flyaway Council: Atlantic Flyaway Mute Swan Management
Plan 2003-2013. Prepared by the Snow Goose, Brant and Swan
Committee. Jul 2003. http://www.dnr.state.md.us/wildlife/afcmuteplan.html
Day, L. The City Naturalist – Mute Swan. NY Site: West
Side. 79th Street Boat Basin Flora and Fuana Society. 1996. http://www.nysite.com/nature/fauna/swan.htm
Hindman, L. J. Mute Swan: Beautiful but Controversial Birds. http://www.dnr.state.md.us/wildlife/muteswans.html
Ivory, A. 2002. Cygnus olor (mute swan), Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Cygnus_olor.html
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. http://www.chesapeakebay.net/pubs/calendar/NISW_12-10-03_Report_6_5129.pdf
O’Connell, K. A. Mute Swans Spark Loud Debate in Chesapeake Bay.
05 Jun 2003. National Geographic News. http://news.nationalgeographic.com/news/2003/06/0605_030605_muteswan.html
Petrie, S. A. and C. M. Francis. Rapid Increase in the Great Lakes
Population of Mute Swans. http://www.kwic.com/~longpointbio/mswan/mswan.htm
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. http://www.bsc-eoc.org/lpbo/lpwwrfmuteswan.html
Swans at Berwick: Mute Swans. http://freepages.genealogy.rootsweb.com/~agene/swan.htm
Map taken from: Mute Swan
Cygnus olor: Map of Winter Distribution from CBC. http://www.mbr-pwrc.usgs.gov/bbs/cbcra/h1782ra.html
Author and Photographs: Meredith Walsh
Last Edited: November 21, 2004
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