Two species of swans - tundra and mute - winter on the Chesapeake Bay. But only the tundra swan, formerly known as the whistling swan, is native to North American. Tundra swans are large white birds, weighing an average of 14 to 16 pounds, with b lack legs and feet. A small yellow spot in front of the eye marks the base of its mostly black bill. A long neck, as long as its body, is held straight or slightly curved.
Tundra swans are monogamous, forming pairs in autumn. In spring, they leave their wintering areas and return to the arctic and subarctic regions of North America and northeastern Siberia. From May to June, they nest on islets, peninsulas and elev ated hummocks of the open tundra.
Male swans (cobs) and female swans (pens) make their nest out of mosses, grasses and sedges, often leaving it surrounded by a ring of open water as they pull up the vegetation. A pen will lay 3 to 4 eggs that she will incubate for 35 to 40 days, although the cob may sit on the nest while she feeds, mostly at night. Both parents will tend and guard the young (cygnets) which are born precocial, meaning they are covered in down and are mobile, following their parents to find their own food. The young are ready to fly after two months.
Tundra swans winter across the United States. Those that come to the Bay make the longest migration of any other Chesapeake waterfowl; some traveling more than 4,000 miles. Tundra swans from as far away as the Bering Sea and the Arctic Ocean, fly east over Canada and then southeast to the Bay. They migrate in a flock made of several family units, flying in a "V"-formation or in lines. The wing beat is slow and steady. The high pitched, mellow "hoo-hoo" call of tundra swans is often heard before t he flock can be seen. They arrive during October and November and usually flock by themselves away from other birds.
Until recently, the Chesapeake Bay was the most important wintering area on the Atlantic Coast for tundra swans. During the late 1960s, more than 40,000 tundra swans wintered on Bay. But today, more than half of the tundra swan population along t he Atlantic Coast winters in North Carolina. The decline of submerged aquatic vegetation throughout the Chesapeake is believed to be the cause of the southern shift of wintering tundra swans.The preferred foods of wintering tundra swans are the tubers roo ts and leaves of SAV and marsh plants. As the grasses disappeared during the 1970s, tundra swans, like many other waterfowl, began feeding in farm fields on waste grains, such as corn and soybeans, as well as winter wheat and barley. Tundra swans may fly 15 miles inland to feed.
The other swan species inhabiting the Bay, the mute swan, may be more familiar to us, but it is an unwelcome intruder. These large, aggressive birds were brought to North American parks and zoos during the mid-1900s. The feral population of mut e swans on Chesapeake Bay became established after several birds escaped captivity.
A native of Eurasia, the mute swan weighs average of 21 to 25 pounds, has a wing span of 5 feet or more and is recognized by a knobbed bill. The knob is black at the base and around the eye. The rest of the bill is pink, becoming orange-red durin g breeding season. A long, curved, "S"-shaped neck also characterizes the mute swan.
Unlike the tundra swan, the mute swan is a year-round resident of the Bay. Both the male and female share the task of building a nest. The nest is located on the ground and near water and is made of cattails, reeds and roots lined with down. The female incubates the 4 to 8 eggs for 35 to 41 days. Upon hatching, young mute swans, like tundra swans, are mobile and follow their parents to find food.
Mute swans threaten other native wildlife throughout the year. They drive out waterfowl, such as the black duck, by taking over breeding areas. They will harass waterbirds, chasing them away from the island habitats used for breeding.
By 1993, a large molting flock of young mute swans had eliminated the only nesting colony of black skimmers (a threatened species in Maryland) established in the Maryland portion of the Chesapeake Bay. This same flock of mute swans prevent least terns (a species in need of special protection) from nesting on the oyster shell bars and beaches of Tar Bay in Dorchester County. The mute swans congregate in such large numbers that they trample both eggs and young.
More than 95 percent of the mute swans's diet is made of aquatic vegetation. Unlike other waterfowl such as tundra swans geese and ducks, mute swan do not nibble seeds and tubers of submerged aquatic vegetation. Instead, they rip out the entire p lant and its root system, stripping the bottom of valuable SAV that is needed as food by other waterfowl and as habitat for other living resources such as blue crabs. Approximately 2,000 mute swans inhabit the Bay, with the majority of the population in Dorchester County and Eastern Bay, Maryland. In the absence of control measures, it is expected that the number of feral mute swans will more than double by the year 2000. Wildlife officials are looking at ways to stabilize the feral mute swan population.
Approximately 1 million waterfowl including tundra swans, Canada geese, snow geese, canvasbacks, mallards, black ducks, scoters and oldsquaw winter on the Chesapeake Bay. They all depend on protected, undisturbed areas and plentiful food sources to survive the cold months and return to breeding grounds in the spring. By controlling exotic species, obeying hunting limits and preserving wetlands, SAV beds and other shallow water habitats, we can ensure that flocks of waterfowl will continue to grac e our winter landscape.