Wednesday, December 22, 2010

Eight Swans

The twelve days of Christmas are not quite underway, although today I saw eight swans-a-flying. Okay, so not quite seven swans-a-swimming, but these were mute swans which I think is the featured species in the classic carol.

Kodi and I were on our walkabout near the Exeter River when I heard a soft hum overhead. I was thinking a muffled flock of Canada geese, until I saw the eight swans with pure white bodies and incredibly long, graceful necks. Swans must be one of the most beautiful birds to see in flight and to see eight was a treat. According to the Sibley Guide to Birds, mute swan wings produce loud, resonant, throbbing hum in flight, unlike other swans. So, their wings make a singing sound -- maybe it should have been seven swans-a-flying.

Something not quite so musical is that mute swans are considered a nuisance. Biologists all along the East coast treat them as a pest. Native to Europe and Asia, the mute swan has adapted well to the New World after it was introduced here in the late 1800s to grace lakes and ponds as a living ornament. Strongly territorial, mute swans aggressively defend their nest site from anything -- ducks and geese, humans, predators. Hence the concern that they drive off native wetland birds that are trying to nest in the same vicinity. Also, because of their large size they eat large quantities of aquatic plants, further impacting the habitat for native ducks and geese.

Many state agencies work actively to reduce the numbers of mute swans. A common technique is to shake or "addle" the eggs in a nest, which kills the developing embryo and fools the swans into continuing to sit on the nest. It seems harsh perhaps, but the goal is to get the population size down to some equilibrium where it has less impact on native wetlands and bird life. If you are really curious about what states are doing related to mute swans read the mute swan management plan.

As a biologist I think it is okay for states to control mute swans, just as many of us work to remove invasive plants. We will never get rid of every last buckthorn or multiflora rose or Japanese knotweed or mute swan, but we can control the spread of these exotics and provide room for native plants and animals to thrive.

Still, maybe because it is the Christmas season, it was neat see those graceful eight swans-a-flying (as long as there are not too many more!).

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