Trumpeter Swans in Yellowstone National Park
The Trumpeter Swan is the largest native North American bird, if measured in terms of weight and length, and is (on average) the largest waterfowl species on earth.
Yellowstone National Park is home to two different populations of trumpeter swans. The first is a group of less than 25 birds that lives in the region year-round. The second is a highly migratory population that visits the park only during the winter. The number of migratory swans has grown, while the number of resident birds has declined and shows signs of being a species at risk.
Look for trumpeter swans along the Madison and Firehole rivers, and along the Yellowstone River, south of Canyon.
Trumpeter Swan (Cygnus Buccinator)
Trumpeter swans males are called cobs and typically measure from 57-64 inches and weigh 26 pound. Females are called pens and they typically range from 55-60 inches and weigh 22 pounds.
Trumpeter swans have white plumage with a long neck, a black bill subtly marked with salmon-pink along the mouth line, and short black legs. They have a wingspan of almost 10 feet!
These birds feed while swimming, sometimes up-ending or dabbling to reach submerged food. The diet is almost entirely aquatic plants. In winter, they may also eat grasses and grains in fields. The young (cygnets) are fed on insects and small crustaceans along with plants at first, changing to a vegetation-based diet over the first few months.
Adults go through a summer molt when they temporarily lose their flight feathers. The females become flightless shortly after the young hatch; the males go through this process about a month later when the females have completed their molt.
Their breeding habitat is in large shallow ponds and wide slow rivers. The female lays three to ten eggs in a mound of plant material on a small island, a beaver or muskrat lodge, or a floating platform. The same location may be used for several years. The eggs average 2.9 inches wide, 4.5 inches long, and weigh about 11.3 ounces.
The incubation period is 32 to 37 days. These birds often mate for life, and both parents will participate in raising the cygnets, but only the female will incubate the eggs.
The cygnets are grey in appearance, becoming white after their first year. Traditionally, the Centennial Valley of Montana has been a hot spot for cygnet production in the greater Yellowstone area.
The young are able to swim within two days and usually are capable of feeding themselves after about two weeks. The fledging stage is reached at three to four months.
Predators of Trumpeter Swan eggs and cygnets include raven, raccoon, bear and wolf. Larger cygnets and nesting adults are preyed on by Golden Eagle, Lynx and Coyote . Few predators, apart from the Bobcat and possibly the Golden Eagle, are capable of taking adults when they are not nesting.
The trumpeter swan was named after its call which some observers have described as resonant, deep, loud, and trumpet-like. The E.B. White novel, The Trumpet of the Swan is about a trumpeter swan which learns to play the trumpet in order to compensate for having been born mute.
Trumpeter Swan of the Past, Present and Future
Trumpeter Swans were once fairly common throughout the United States but in the 1800s and early 1900s, the game hunting and millinery trade rapidly depleted nesting populations. Swan skins were in demand in Europe where they were used to make ladies' powder puffs and swan feathers were used to adorn fashionable hats.
A small group of Trumpeter Swans survived into the twentieth century hidden away in the vast wilderness of Yellowstone Park. The swan population began to recover through conservation efforts. Protected areas have been essential to the trumpeter swan ’s survival and the greater Yellowstone ecosystem contains suitable habitat for these birds.
Yellowstone was once the trumpeter swans' last stronghold yet the greater Yellowstone population has declined in recent years. The summer nesting population in the park, which numbered 45 swans at times during the 1980s, rarely exceeds 25 now. The winter population, boosted by migrant birds from elsewhere in greater Yellowstone and from Canada, has varied from 60 to several hundred swans.
Human activities have sometimes affected Trumpeter Swan reproduction. Many signs are posted and patrol rangers enforce regulations that prohibit people from approaching within 25 yards but the beautiful and highly visible trumpeter pairs attract visitors who approach closely to take photos and offer food. When swans become habituated to people, they lose their fear of predators and are more likely to die from predation. In certain areas, biologists have attempted to improve trumpeter swan nesting success by providing floating platforms.
Swan recruitment from outside of Yellowstone National Park is another critical factor in maintaining the resident swan population. Historically, swans that died in the park (mainly through predation) were eventually replaced by swans from outside the park (namely the Centennial Valley). Yellowstone Park established a Trumpeter Swan Recovery Fund in 1989 which has raised public awareness and support for swan conservation and nesting sites.
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