Thursday, February 14, 2013

Mute Swans

On Tuesday, a friend and I snowshoed at Wagon Hill Farm in Durham. A conservation area with extensive frontage on the Great Bay estuary. In winter it is common to see a pair or two of buffleheads bobbing and diving just off-shore, as we did this week. The bufflehead is a small, round duck that winters along our coast and in bays, then heads to far northern Canada to breed and nest in old woodpecker holes. The male has a large patch of white on the back of its glossy purple and green head.

While we watched the bufflehead, a large flock of Canada geese floated out from a small cove. Great Bay is a major winter refuge for ducks and geese, with 5,000 to 10,000 spending the winter. Buffleheads and other "diving ducks" dive down to feed on clams in the soft mud. The geese feed on eelgrass roots at low tide and fly off to cornfields during the day to find waste grain.

We stood looking out at the shimmering water, then noticed three large white birds floating in the water just off-shore to our right. These were mute swans. Buffleheads are small and cute, and a welcome winter visitor to the Bay. Mute swans are big and beautiful, but non-native, and therefore not so welcome in the Bay.
Mute swans cause trouble to native birds in a couple ways. They are highly territorial, chasing away all intruders from the bay, pond, or marsh where they nest. This makes good nesting habitat off-limits for native ducks and geese. Also, if you ever tried to canoe near a mute swan nest, you should know how to swiftly paddle away, as they will attack the canoe with their strong wings.

Adults hold their wings raised over their back when they swim, some suggest it is an aggressive posture. One of the three that we saw was swimming near shore with wings raised, keeping a close eye on Kodi as he wandered down to the water's edge.
Mute swans eat a lot of vegetation, pulling up vast amounts of aquatic plants by their roots, which can be destructive to the habitat. Around 1910, mute swans were introduced from Europe to adorn parks and estates in the lower Hudson River Valley. By 1936 they were living in the wild and their population has expanded up and down the east coast ever since. State wildlife agencies attempt to control their populations through removal of adults and shaking ("addling") eggs in the nest.

The mute swan's size, pure white body, and orange bill with a big black knob at the base are distinctive. They swim with their neck slightly curved and their bill pointing down. When they swim with their wings raised they do look like a water ornament. But perhaps one we could do without in the Great Bay.

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