Trumpeter Swan
Order: Anseriformes
Family: Anatidae
Genus/Species: Cygnus buccinator
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| Photo by Jessie Cohen, NZP |
Description
The majestic Trumpeter Swan is the largest of all North American Waterfowl. They average 1.5 m in length, weigh 11-15 kg, and have a wing span of 2.4 to 3 m. Trumpeter swans are pure white with black legs and large flat black bills. A salmon-red "lipstick line" divides the upper and lower mandibles of the bill. The feathers of the head and neck may become stained a pale rust color from feeding in iron rich northern lakes. Their extraordinarily long coiled tracheas allow them to produce a deep resonant trumpeting call that has been compared to the blare of a French taxi cab horn. Juvenile swans are a grayish brown their first winter, not achieving adult plumage until late in their second year.
Distribution and Habitat
Trumpeter Swans are divided into three main populations. The largest group, the Pacific Coast Population (15,000 birds), breeds in Alaska and western Canada, wintering south to the Columbia River. The Rocky Mountain Population (2,500 birds) has two separate sub-populations. A year-round resident flock centers around the Red Rock Lakes National Wildlife Refuge in Montana and a Canadian flock migrates into the same region for the winter. The Interior Population (900 birds), including all Trumpeter Swans east of the Rocky Mountains, is the product of over thirty years of reintroduction efforts.
In the summer swans occupy swamps, marshes, and shallow forested lakes. They are very sensitive to human activity and will readily abandon prime habitat when disturbed. In the winter they need ice-free water in order to find enough food to survive. The coastal populations find suitable wintering habitat in estuaries and sheltered coastlines. Severe weather forces the Rocky Mountain flock to concentrate in the Greater Yellowstone Ecosystem where geothermal activity prevents freezing.
Diet
Adult swans are almost exclusively vegetarian. Their long necks reach plant leaves and stems well below the surface. Powerful feet enable them to dig up the lake bottoms in search of hidden roots and shoots. Their favorite foods are; waterweed, sago pondweed, water milfoil and duck potato. Newly hatched cygnets feed primarily on water beetles and small crustaceans for their first three weeks, gradually shifting over to a more vegetarian fare by five weeks of age.
Reproduction
Trumpeter Swans mate for life. Two to three year old birds begin their courtship on the wintering grounds. The courtship ritual includes synchronized swimming, bill dipping, blowing in the water, and dueting. The young couples may not nest for another year or two. Breeding pairs arrive on their nesting grounds to establish and defend large territories (70-400 acres) before all the ice has melted. They prefer sizable bodies of water with an ample supply of food plants, dense surrounding vegetation for privacy, and plenty of room for take-offs.
Nest building begins soon after arrival, with the refurbishing of last year's nest or the selection of a new site. Trumpeters often build on top of muskrat houses or beaver lodges. They uproot surrounding vegetation clearing a moat for visibility and building up the center until the final product measures up to 2.5 m across and rises 40 cm above the water line. The female lays 3-9 large off-white eggs. She incubates for 33-35 days, leaving the nest only for short periods to forage. The male swims nearby, guarding against predators.
Fluffy pale gray down covers the newly hatched cygnets. They leave the nest after a day or two to begin to feed themselves. The parents help them by breaking plant material off so that it floats to the surface where the buoyant youngsters can reach it. Many cygnets succumb to cold, wet weather, parasites, insufficient food, or predators. It is normal for each family to lose nearly half of the clutch. The first feathers emerge after one month, and at 10 weeks they are fully feathered in a light brownish-gray. By 15 weeks, they have reached a weight of 9 kg and are learning to fly. Northern breeders have very little time to perfect flight before they must leave the rapidly freezing lakes for wintering grounds.
Conservation
Prior to the 19th century Trumpeter Swans were fairly common all across the northern prairies. Then they fell victim to the millinery trade and market hunting. By the close of the century many people believed them to be extinct. A small resident population was discovered in remote western Montana (Red Rock Lakes), but even that had dwindled to a mere 69 birds in 1932. The much larger Alaskan population was unknown to science until the 1950's. In 1935 the U.S. Government established the Red Rock Lakes National Wildlife Refuge for the express purpose of saving the Trumpeter Swan. Refuge personnel quickly improved the habitat by restricting livestock grazing and hay cutting, protecting the muskrats whose houses the swans used for nest sites, controlling predators, and augmenting winter food supplies. They are now legally protected from hunting throughout their range. By the end of the 1950's the local population had increased to 640 birds.
By 1992, 90% of the Rocky Mountain population concentrated within a 30 mile radius of Red Rock Lakes. Managers discontinued supplemental feeding when they decided that it was supporting artificially high numbers of birds in a small area, increasing the risk of a catastrophic disease outbreak. Biologists feel that many independent populations of swans, spread out over a larger portion of their former range, offer a better long term chance of survival for the species. Relocation programs have returned Trumpeter Swans to Minnesota, Wisconsin, Michigan, Iowa and Ontario. There are plans to underway to establish a migratory flock in the Chesapeake Bay area, bringing the Trumpeter all the way back to the east coast. As successful as these restoration efforts have been in the long run, they have suffered numerous setbacks caused by lead poisoning, illegal shooting, power line collisions, loss of suitable habitat, and uncertain funding.
References
Del Hoyo, J., Elliot, A. and J. Sargatal. eds. 1992. Handbook of the Birds of the World. Vol. 1. Ostrich to Ducks. Lynx Edicions, Barcelona.
Ehrlich, P. R., Dobkin, D. S., and D. Wheye. 1992. Birds in Jeopardy. Stanford University Press, Stanford.
Matteson, S. and S. Craven. 1995. The Trumpeter Swan. USDA publication #G3647
Todd, F. S. 1996. Natural History of the Waterfowl. Ibis Publishing Co., San Diego, CA.
Please note: There are no longer any of these birds at the Zoo.
