Trumpeter Swans Threatened by Foreign Species
Populations of Aggressive Feral Swans are Increasing Rapidly
Jul 26, 2009
The trumpeter swan (Cygnus buccinator) is the largest waterfowl species in North America, weighing 10 to 12 kilograms. These majestic birds are pure white with black feet and bills.
Trumpeter swans once nested throughout Canada and wintered anywhere from southern Canada to the Gulf of Mexico. But hunting for their meat and feathers took a heavy toll. Trumpeters completely disappeared in Ontario in 1886, when the last one was shot at Long Point on Lake Erie. Although trumpeter swans became a protected species in 1916, by 1933, there were only 77 of breeding age in all of Canada and just 50 in the United States.
Trumpeter Swan Populations Recovering
Today, trumpeter swan populations are rebounding. A restoration project begun in southern Ontario in 1982 has resulted in a self-sustaining, but mostly non-migrating, population of about a thousand trumpeters in 2009. There are now about 16,000 wild trumpeter swans in North America.
Trumpeter swans usually mate for life and often use the same nesting site and food sources every year unless something forces them to change their pattern. Their offspring, called cygnets, learn migration routes and food sources from their parents. In the wild, trumpeters generally live about 12 years, but can live as long as 25 to 35 years.
In southern Ontario, trumpeters often mingle with mute swans (Cygnus olor), which are native to Europe and Asia. The two species also occasionally interbreed, producing hybrid swans, which is counter-productive for conserving the rare trumpeter.
Mute Swans Increasing in Numbers
Mute swans were introduced to North America as captive birds. By 1910, there were feral mute swans breeding along New York’s Hudson River. Since about 1940, their numbers have been increasing steadily. In the 1950s, some were released into the wild in Ontario, and the first feral breeding pair in Ontario was recorded in 1958.
Mute swans can be distinguished from North American swans by their bright orange bills with a black knob at the base. Numbers of this introduced species are growing so rapidly that they may soon be out-competing the native swans for the best food and nesting sites. They are notoriously aggressive and have been known to drown dogs and attack and injure people.
Dr. Scott A. Petrie is Research Director of Long Point Waterfowl and a lecturer on Wildlife Ecology and Management at the University of Western Ontario. He has studied mute swan populations in the Great Lakes region of Ontario, and he is concerned about the effect these birds will have on native swans, geese and ducks.
“Several aspects of their ecology suggests that mute swans could be a particularly serious problem,” Petrie noted. “They are extremely aggressive, and occupy and defend large parcels of wetland habitat during the breeding season. They not only can displace native waterfowl from breeding and staging habitats, but have also been reported to kill adult and juvenile ducks, geese, and other waterbirds that enter their territories.”
He said mute swan populations are increasing as much as 30 per cent annually, and warned, “Mute swans are likely to pose a serious threat to native species of waterfowl and the integrity of the ecosystem if their populations are allowed to continue growing.”
He has suggested that mute swans be removed from the list of protected species in Canada and that the feral populations be controlled through culling or hunting to protect native species, in particular the majestic trumpeter swan, which so recently was in danger of vanishing altogether.
References:
Hinterland Who’s Who: Trumpeter Swan
Petrie, Scott A., and Charles M. Francis. “Rapid Increase in The
Great Lakes Population of Mute Swans”. Bird Studies Canada, PO Box 160, Port Rowan, Ontario N0E 1M0.
“Swans in Cootes Paradise”. McMaster University Faculty of Science, Hamilton, Ontario, 1993.
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