Sunday, April 29, 2018

Mute Swans: An Adorable Invasive Species

swan by Adelaide TyrolThe big white birds paddling gracefully across a Massachusetts pond last November surprised me. I’d grown up in the town I was visiting and had never seen swans there, although my friend assured me they were resident birds. The only mute swans I’d seen before, years ago, were floating along the River Thames between Eton College and Windsor Castle.

Swans in England have a long history, and the mute swans along the Thames are, by law, the property of the queen. Mute swans on our side of the Atlantic are a more modern phenomenon and have no such protection. In fact, wildlife managers have been working for years to reduce the population of this species in order to protect native habitat and waterfowl.

While tundra swans and trumpeter swans, both native to North America, occasionally pass through our region on their way to and from northern breeding grounds, the larger mute swans are not native. They were introduced as adornments to parks and estate ponds in the nineteenth century and have since made their feral way from the Chesapeake Bay to the Midwest and the Pacific Northwest.

Mute swans are among the largest birds in North America. Males weigh up to 30 pounds and measure more than four feet from beak to tail, with a wingspan stretching toward eight feet. They are beautiful birds, with pure white feathers and s-curved necks, but their impact on native habitat and other waterfowl is less appealing.

“They raise havoc with the native species,” said Jessica Carloni, Waterfowl Project Leader for the New Hampshire Fish and Game Department.

Voracious and aggressively territorial, mute swans eat up to eight pounds of aquatic plants each day, uprooting several more pounds as they forage. They skim plants from the surface of water, and also rake the bottom with their feet to bring up additional vegetation. They can consume plants – grasses, pondweeds, and others – faster than the plants are able to recover.

Mute swans establish breeding territories on fresh, brackish, and saltwater ponds, as well as slow-moving rivers, bogs, and inland streams. Despite their serene posture on the water, these birds do not play nicely with others and are unlikely to share territory with other species of waterfowl. Besides chasing ducks, geese, and gulls away from their nesting sites, mute swans will also go after dogs and humans who wander too close to a nest.

One of the reasons that people have a fondness for these birds is their tendency to remain in pair bonds over multiple years. They build their homes together, with the male identifying multiple potential nest sites, and the female having the final say in where they settle down. The male begins the nest construction by assembling a platform of crisscrossed vegetation, then collects additional materials – reeds, twigs, cattails, sedges, and grasses – for the female to continue the building, piling the materials onto the nest and using her feet and body to form a custom-molded concavity in a nest that may be five feet across and two feet high. Both male and female may add to the nest during egg-laying and while brooding chicks.

Their population, estimated at fewer than 1,000 in 1950, climbed significantly from the mid-1900s to the turn of the twenty-first century. The reference book Ducks, Geese, and Swans of North America by Guy A. Baldassarre estimates some 13,650 mute swans living in the Atlantic Flyway – the migratory channel running from Eastern Canada to Florida – in 2005, with populations dropping to 10,500 in 2008 and to 9,700 by 2011.

The recent drop is likely the result of efforts to stop mute swans from reproducing, as well as active culling of the species. Several states along the Atlantic Flyway – including Maryland and New York, where mute swans have decimated populations of skimmers and terns – have formal management plans in place, which include lethal action in some instances. Others, like New Hampshire, take a more passive approach, namely discouraging mute swan reproduction by addling eggs in the nest.

“We care about our native waterfowl,” Carloni said. “A lot of folks try to stop invasive vegetation. This is similar.”

Finding ways to knock off purple loosestrife or Japanese knotweed, however, is considerably less controversial than developing a management plan – any management plan – for reducing the number of mute swans. As Carloni noted, “people get really attached to these birds,” and don’t recognize their harm to local ecosystems.

Meghan McCarthy McPhaul is an author and freelance writer. She lives in Franconia, New Hampshire. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine, and sponsored by the Wellborn Ecology Fund of New Hampshire Charitable Foundation.

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The Adirondack Almanack publishes occasional guest essays from Adirondack residents, visitors, and those with an interest in the Adirondack Park. Submissions should be directed to Almanack editor Melissa Hart at

9 Responses

  1. Ethan says:

    There are currently approximately only 2,200 Mute Swans in all of NY State.

    While I acknowledge they may be destructive to some other waterfowl species and vegetation, the DEC should take every precaution to limit expansion via non-lethal means. Which begs the question, when addling eggs, what is the common practice: Do ALL eggs in a nest get oiled? I’m hoping at least one egg per nest is unharmed; anything less would be inhumane and unacceptable.

    “A lot of folks try to stop invasive vegetation. This is similar.”
    (Jessica Carloni, NH Fish and Game)
    Really, Ms. Carloni? Perhaps a search is needed for a different analogy. A weed plucked from a pond does not have a beating heart.

    • Paul says:

      “Only” – 2,200 individuals? 2200 that don’t have their normal population controls around. A recipe for disaster.

  2. Tim-Brunswick says:

    Gimme a break…really!

    Maybe “Ethan” should run around and oil all but one egg per nest. Even getting close to a Mute Swan’s nesting area is extremely dangerous as they will not hesitate to attack with formidable strength in both their wings and beak. There are documented attacks and at least one fatality on humans.

    NYS DEC had a great plan for getting rid of them and thanks to a Governor who bowed to the weeping/bleeding heart birders, they had to back off. They’re invasive…get rid of them!

    Thank you


    • Boreas says:


      What was the plan you mention? Last I knew, DEC hadn’t really decided on a plan – only a few regional experiments. Has any comprehensive, statewide plan ever been instituted? With a migratory species, no control will be very effective unless all states, FEDS, (and landowners) cooperate.

  3. James Bullard says:

    If we want to remove all invasive species perhaps we should start with pigeons, AKA Rock Doves, which were introduced by the colonists and are truly ubiquitous now.

    • John Warren says:

      Who said we want to remove ALL invasive species?

      • JohnL says:

        Not me John. Who (or what) else is going to crap on window ledges, church steeples, silos, and all over barnyards if we get rid of the ubiquitous pigeon, aka rock dove? Too, will something make up the shortfall in Peregrine Falcon food when all pigeons are eliminated. We must think of our predator friends well being too. And lastly, I have many fond memories of helping my local farmer friends eliminate pigeons (via shotgun) from their barns for sanitary reasons. I wouldn’t want to deprive our younger generation of that same experience.

  4. James Bullard says:

    We are ripping out purple loosestrife and many other plants. We are inspecting boats that go from one body of water to another. If some plants or birds are okay, then why pick on swans? BTW, mullein in an introduced invasive too. Again, the colonists are to blame. Who gets to pick and choose what plants or birds don’t belong? I’m way more concerned over climate change than 2200 swans. That is change that will have a huge impact.

    • JohnL says:

      Not me James. The swans concern me more than climate change, global warming, or whatever you call it now. And, unlike global warming, at least with the 2200 swans, we could actually have some impact on them. Besides, we actually DO get to pick and choose what species (plant, animal, insect) should be eliminated. We do it all the time.

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