Weekly Bird Notes: Mute Swan Invasion

With an eight foot wing span, an elegant long neck and white plumage, the mute swan was brought to North America from its native lands in northern and central Eurasia in the late 1800s to grace the ponds of parks and estates. Escaped individuals established breeding populations in several areas, where their aggressive behavior now threatens native wildlife. At least 14,000 mute swans now live along the U.S. Atlantic coast alone, according to the U.S. Fish and Wildlife Service.

Tundra swans and trumpeter swans are the only swans native to North America. Adult tundra and trumpeter swans have white feathers similar to mute swans, but both native species have mostly black bills. Native swans nest primarily in arctic habitats and reside in the eastern United States only during migration and winter.

Mute swans are very aggressive toward native waterfowl and they overgraze wetland vegetation. It is estimated that they eat nine million pounds of vegetation in Maryland each year. They have been found to cause terns to abandon their island nesting colonies and trample their eggs and chicks.

Relative newcomers to Vermont, mute swans have been observed annually here since 1993. They have successfully nested in at least one location and they appear to be establishing populations at other locations. According to the Vermont eBird database, most sightings come from the northern portion of Lake Champlain and the southern Connecticut River valley.

Mute swans first breed at age three. They lay five or six eggs and usually four or five cygnets survive. The life span for a wild mute swan can exceed 25 years, and with few predators, biologists expect that the population will continue to increase without proper management.

Five juvenile mute swans were reported last week at the Grand Isle ferry landing. Seven were found on Lake Wantastiquet in Vernon.

Open water on Lake Champlain provided waterfowl highlights this week. Two harlequin duck and several long-tailed ducks were found at Shelburne Point. A snow goose was seen in Shelburne Bay. A drake northern pintail was found at the Colchester Causeway. Highlights at the South Hero Causeway included 2 male redheads, 2 Barrow’s goldeneyes and a female red-breasted merganser.

Common loons were seen at the Grand Isle ferry landing, Meach Cove and eight at the Charlotte Town Beach. Nineteen bald eagles were observed at the Sandbar Causeway. Both Iceland and glaucous gulls were found at Sandbar Causeway and the Grand Isle ferry landing.

You can explore all the birds reported last week in Vermont and add your own sightings at www.ebird.org/content/vt.