Beauty or beast? Giant white swans a growing invasive threat in Canada.
By WorkCabin.ca Staff
When most people think of invasive species damaging our ecosystem, the first thought turns to a myriad of small bugs eating trees, or exotic plants overrunning terrain. Rarely, if ever, do mute swans grab the attention of average Canadians. But that may soon change as growing evidence shows this giant waterfowl -- which establishes itself as the kingpin of the wild territory it colonizes -- is posing a serious threat to native species and habitat.
Wildlife experts are calling for action before it's too late and the bird establishes itself across Canada.
In an odd twist, mute swans are believed to be the only invasive species protected by law in Canada. That's because general use of the word ‘swans' in federal legislation has inadvertently given mute swans protection that was intended for native species.
Mute swans were introduced to North America from Asia and Europe in the late 1800s for zoos, private collectors, and as regal additions to city parks and waterways. Once these birds started escaping though -- an inevitable result for many imported species -- the seeds of a problem were planted.
Today, there are about 25,000 of the swans in the Great Lakes region, Chesapeake Bay area and North Atlantic coastal areas. That's a dramatic population explosion from 1,000 in the 1950s.
As any wetland kayaker who has had a close encounter with these birds knows, they're highly aggressive. They won't think twice about charging you if you paddle into their territory. Thank goodness a kayak paddle can also serve a handy defensive purpose -- if you know how to use it. Otherwise, you could end up with bruises, cuts, or worse, broken bones. In fact, there have been a few cases of swimmers being drowned by overly-aggressive mute swans. If these swans can pose such risk to humans, imagine their impact on native species.
In Canada, the area of particular concern is the lower Great Lakes region. The area is on the major migration path and a wintering ground for many native Eastern North American bird species. Mute swans compete directly with many of these species for food and desirable habitat. In Maryland alone, the swans are suspected of causing a 40 per cent decline in the number of native tundra swans over the past quarter century. Tundra swans, whose annual migration to and from Canada's Arctic is one of the wonders of nature among birdwatchers in southern Ontario, are unable to find the food they need to survive and can be bullied from their traditional wintering areas. If mute swans numbers continue to grow then they may also affect tundra swan use of migratory resting areas such as the Great Lakes and migration resting areas.
Mute swans also devour or destroy aquatic plants at an alarming rate. One U.S. study found a single swan is capable of eating eight pounds of vegetation in a day, and uprooting another 20 pounds during the feeding process. The result is loss of habitat and a key food source for other waterfowl and aquatic species, including fish.
Populations of mute swans are being closely monitored in Canada by the Canadian Wildlife Service (CWS) and Long Point Waterfowl. Researchers use small airplanes to record numbers in Lake Erie, Lake Ontario and Lake St. Clair. During aerial surveys between 2003 and 2005, it was discovered that the population had doubled, from 1,373 to 2,737 swans. The results of 2008 surveys will likely show another significant increase.
With no natural predators to reduce their numbers, mute swan populations are expected to continue to grow rapidly in Ontario's lower Great Lakes area, the Canadian hotspot for the invasion. Fortunately, the swans have not yet expanded their range into Western Canada or the Maritimes.
Ontario has no current management plan to reduce populations.
Dr. Scott Petrie, Research Director of Long Point Waterfowl and lecturer on Wildlife Ecology and Management at the University of Western Ontario, has studied mute swans and other waterfowl on the Great Lakes.
Petrie feels strongly that if we do not soon start to control this invasive species on the Great Lakes we will soon have a problem of the magnitude now being experienced in the United States.
"Government officials know exactly what is to happen yet little is being done to prevent the problem," says Petrie.
The Atlantic Flyway Council, composed of officials from state and provincial wildlife management agencies along an eastern seaboard migratory zone stretching from Florida to Ontario, Nunavut and the Maritimes, is closely monitoring the swans. The council is calling for a coordinated plan to reduce populations to 3,000 swans by 2013, and increased efforts to educate the public about the serious threat posed by mute swans.
So, the next time you stand by a well manicured city park or waterway and see a giant white swan, all may not be as idyllic as you think.
There's an ugly and growing problem in the wilds of Canada.
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Posted by on 10/20 at 02:45 PM