Mute Swans in North America

Cygnus olor - a Domestic Pest Bird Multiplying in the Wild

Jul 20, 2009 Rosemary Drisdelle

Mute Swans were introduced to North America. Their growing population and spread causes problems for the environment and native species of the Atlantic Flyway.

Mute Swans, Cygnus olor, do not occur naturally in North America. A bird of Europe and Asia, they were brought to North America in the late 1800s and early 1900s and kept in zoos, parks, and estate gardens as ornamental birds. Eventually, of course, some escaped, and some may have been deliberately released into the wild. Today, while North Americans still admire their graceful beauty, scientists know that it would have been better if they had never been introduced.

Feral Mute Swans in North America

Many sources trace the origins of the feral swans of North America to the accidental escape of a few birds in New Jersey in 1916 and in New York in 1919, though it’s unlikely that these were the only instances of accidental or deliberate release. What’s certain is that since early in the twentieth century, Mute Swans have been living and breeding in the wild and their numbers have been steadily growing. Today, they are found from Southern Ontario to Florida, and from the Atlantic coast to the Mississippi River.

How Many Mute Swans are There in North America?

A 2002 survey estimated the population of Mute Swans in the Atlantic Flyway at more than 14,000, approximately double the estimate for just sixteen years earlier. In some areas, surveys show that populations increase by 10% to 30% each year, doubling in just three to seven years. And projections for Southern Ontario, where Mute Swans have been breeding since 1958, indicate there could be 50,000 of the birds there by the middle of this century if the population isn’t controlled.

The Problem With Mute Swans

Most people find Mute Swans beautiful, but there are problems with the growing numbers in North America, mostly with respect to the birds’ impact on native species:

• While breeding, pairs aggressively occupy large areas of wetland and defend their territory against intruders, including native birds that rely on the same wetland for breeding.
• Mute Swans are aggressive - so much so that they kill other types of birds or drive them off their natural territory.
• Mute Swans sometimes interbreed with native swan species: Tundra Swans and Trumpeter Swans.
• Because of their large size and bold nature, these swans sometimes injure both wild and domestic animals, and even people.
• While feeding, the birds tend to uproot plants, damaging river and lake bottoms and spoiling wetlands that other species depend on for habitat, breeding territory, and food.

Controlling Mute Swans

Although the general public still tends to defend Mute Swans, citing their beauty and cultural significance, wildlife specialists and conservation groups are increasingly calling for control of Mute Swan populations in North America. Some studies have resulted in the recommendation to remove 30 – 40% of the birds annually:

• One method of control is to locate nests and treat the eggs so that they don’t hatch. This method is labor intensive and seems not to work very well.
• Deliberately culling (killing significant numbers) is more effective but is particularly distasteful to the public and to animal rights defenders.
• Allowing hunters to take Mute Swans during the hunting season would likely bring populations down.

Those proposing population control don’t aim to exterminate Mute Swans from North America; the objective is to lower the numbers so that people can still enjoy the birds but there is minimal impact on native species and the environment. With luck, we'll be able to enjoy this beautiful bird without sacrificing North America's birds and other biodiversity.

Sources

“Cygnus olor: Mute Swan.” Animal Diversity Web: University of Michigan Museum of Zoology. animaldiversity.ummz.umich.edu

“Mute Swan: An Invasive Species And Its Management In Rhode Island.” Allin, Charles C. Rhode Island Fish and Wildlife. www.dem.ri.gov

“Rapid Increase in The Great Lakes Population of Mute Swans.” Petrie, Scott A. and Charles M. Francis, Bird Studies Canada

The copyright of the article Mute Swans in North America in Birds is owned by Rosemary Drisdelle. Permission to republish Mute Swans in North America in print or online must be granted by the author in writing.

A Mute Swan in New Jersey

A Mute Swan Nesting in Michigan