Trumpeter Swan

Trumpeter Swan
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Anseriformes
Family:	Anatidae
Subfamily:	Anserinae
Tribe:	Cygnini
Genus:	Cygnus
Species:	C. buccinator
Binomial name
Cygnus buccinator Richardson, 1832

The Trumpeter Swan (Cygnus buccinator) is the heaviest bird native to North America and is, on average, the largest extant waterfowl species on earth.^[2] It is the North American counterpart and a close relative of the Whooper Swan of Eurasia, and even has been considered the same species by some authorities.^[3]

Description

Juvenile at the Cincinnati Zoo

Its black bill is useful in distinguishing the Trumpeter Swan from other species

Plate 406 of the Birds of America by John James Audubon, depicting the Trumpeter Swan

The Trumpeter Swan is the largest extant species of waterfowl. Adults usually measure 138–165 cm (54–65 in) long, though large males can range up to 180 cm (71 in) or more.^[2][4][5][6] The weight of adult birds is typically 7–13.6 kg (15–30 lb), with an average weight in males of 11.9 kg (26 lb) and 9.4 kg (21 lb) in females.^[2][7] The wingspan ranges from 185 to 250 cm (73 to 98 in), with the individual wing chords measuring 60–68 cm (24–27 in).^[2][4][5] The largest known male Trumpeter attained a length of 183 cm (72 in), a wingspan of 3.1 m (10 ft) and a weight of 17.2 kg (38 lb).^[8]

The adult Trumpeter Swan is all white in plumage. As with a Whooper Swan, this species has upright posture and a straight neck at all times. The Trumpeter Swan has a large, wedge-shaped black bill that can, in some cases, be minimally lined with salmon-pink coloration around the mouth. The bill measures 10.5–12 cm (4.1–4.7 in) and is up to twice the length of a Canada Goose's (Branta canadensis) bill. The legs are gray-pink in color, though in some birds can appear yellowish gray to even black. The tarsus measures 10.5–12 cm (4.1–4.7 in). The cygnets (juveniles) are grey in appearance, becoming white after the first year.

The Mute Swan (C. olor), introduced to North America, is scarcely smaller. However, it can easily be distinguished by its orange bill and different physical structure (particularly the neck, which is always curved down as opposed to straight in the Trumpeter). The Mute Swan is often found in developed areas near human habitation in North America, whereas Trumpeters are usually only found in pristine wetlands with minimal human disturbance.^[2] The Tundra Swan (C. columbianus) more closely resembles the Trumpeter, but is significantly smaller. The neck of a male Trumpeter may be twice as long as the neck of a Tundra Swan.^[2] The Tundra Swan can be further distinguished by its yellow lores. However, some Trumpeter Swans have yellow lores; many of these individuals appear to be leucistic and have paler legs than typical Trumpeters.^[9] Distinguishing Tundra and Trumpeter Swans from a distance (when size is harder to gauge) is quite challenging, and can often be done only with experience and knowledge of structural details.

Range and habitat

In winter, they may eat crop remnants in agricultural fields, but more commonly they feed while swimming

Their breeding habitat is large shallow ponds, undisturbed lakes, pristine wetlands and wide slow rivers, and marshes in northwestern and central North America, with the largest numbers of breeding pairs found in Alaska. They prefer nesting sites with enough space for them to have enough surface water for them to take off, as well as accessible food, shallow, unpolluted water, and little or no human disturbance.^[10] Natural populations of these swans migrate to and from the Pacific coast and portions of the United States, flying in V-shaped flocks. Released populations are mostly non-migratory. In the winter they migrate to the southern tier of Canada, the eastern part of the northwest states in the United States, especially to the Red Rock Lakes area of Montana, the north Puget Sound region of northwest Washington state;^[11] they have even been observed as far south as Pagosa Springs, Colorado. Historically they range as far south as Texas and southern California.^[12] Since 1992 Trumpeter Swans have been found in Arkansas each November – February on Magness Lake outside of Heber Springs.^[13]

Diet

These birds feed while swimming, sometimes up-ending or dabbling to reach submerged food. The diet is almost entirely aquatic plants. They will eat both the leaves and stems of submerged and emergent vegetation. They will also dig into muddy substrate underwater to extract roots and tubers. In winter, they may also eat grasses and grains in fields. They will often feed at night as well as by day. Feeding activity, and the birds' weights, often peaks in the spring as they prepare for the breeding season.^[14] The young are fed on insects, small fish, fish eggs and small crustaceans along with plants initially, providing additional protein, changing to a vegetation-based diet over the first few months.

Breeding

Trumpeter Swan brood

Trumpeter Swans often mate for life, and both parents participate in raising their young, but primarily the female incubates the eggs. Most pair bonds are formed when swans are 4 to 7 years old, although some pairs do not form until they are nearly 20 years old. "Divorces" have been known between birds, in which case the mates will be serially monogamous, with mates in differing breeding seasons. Occasionally, if his mate dies, a male Trumpeter Swan may not pair again for the rest of his life.^[10] Most egg laying occurs between late April and May. The female lays 3–12 eggs, with 4 to 6 being average, in a mound of plant material on a small island, a beaver or muskrat lodge, or a floating platform on a clump of emergent vegetation. The same location may be used for several years and both members of the pair help build the nest.^[10] The nest consists of a large, open bowl of grasses, sedges and various aquatic vegetation and have ranged in diameter from 1.2 to 3.6 m (3.9 to 11.8 ft), the latter after repeated uses.^[15] The eggs average 73 millimetres (2.9 in) wide, 113.5 millimetres (4.5 in) long, and weigh about 320 grams (11.3 oz).^[10] The incubation period is 32 to 37 days, mainly by the female, although occasionally by the male as well. The young are able to swim within two days and usually are capable of feeding themselves after at most two weeks. The fledging stage is reached at roughly 3 to 4 months.^[16] While nesting, Trumpeter Swans are territorial and harass other animals, including conspecifics, who enter the area of their nest.^[10]

Adults go through a summer moult 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 moult.

Mortality

In captivity, this species has survived to 33 years old and, in the wild, has lived to at least 24 years. Young Trumpeter Swans may have as little as 40% chance of survival, due variously to disturbance and destruction by humans, predation, nest flooding and starvation. In some areas, though, the breeding success rate is considerably greater and, occasionally, all cygnets may reach maturity. Mortality in adults is quite low, usually being 80–100% annually, unless they are hunted by humans.^[17] Predators of Trumpeter Swan eggs include Common Raven (Corvus corax), Common Raccoon (Procyon lotor), Wolverine (Gulo gulo), American Black Bear (Ursus americanus), Brown Bear (Ursus arctos), Coyote (Canis latrans), Gray Wolf (Canis lupus) and Northern River Otter (Lontra canadensis). Nest location can provide partial protection from most mammalian nest predators, especially if placed on islands or floating vegetation in deep waters. Most of the same predators will prey on young cygnets, as will Common Snapping Turtle (Chelhydra serpentina), California Gull (Larus californicus), Great Horned Owl (Bubo virginianus) and American Mink (Mustela vison). Larger cygnets and, rarely, nesting adults may be ambushed by Golden Eagle (Aquila chrysaetos), Bobcat (Lynx rufus), Red Fox (Vulpes vulpes) and Coyote. When their eggs and young are threatened, the parents can be quite aggressive, initially displaying with head bobbing and hissing. If this is not sufficient, the adults will physically combat the predator, battering with their powerful wings and chomping down with their large bills, and have managed to kill predators equal to their own weight in confrontations.^[18] Predation of adults when they are not nesting is rare, although they may possibly be hunted by Golden and Bald Eagles. Photos of a Bald Eagle (Haliaeetus leucocephalus) exceptionally attacking an adult Trumpeter Swan in mid-flight were taken recently, although the swan managed to survive the predation attempt.^[19]

Conservation status

Three flying in Missouri, USA

Wintering in British Columbia, Canada

In the 19th and early 20th centuries, the Trumpeter Swan was hunted heavily, both as game and a source of feathers. This species is also unusually sensitive to lead poisoning while young. These birds once bred in North America from northwestern Indiana west to Oregon in the U.S., and in Canada from James Bay to the Yukon, and they migrated as far south as Texas and southern California.^[12] The trumpeter was rare or extinct in most of the United States by the early twentieth century.^[12] Many thousands survived in the core range in Canada and Alaska, however, where populations have since rebounded. One of the largest conservation sites for the Trumpeter Swan is located in Lois Hole Provincial Park. It is located adjacent to the renamed Trumpeter subdivision of Edmonton, Alberta within Big Lake.

Early efforts to reintroduce this bird into other parts of its original range, and to introduce it elsewhere, have had only modest success, as suitable habitats have dwindled and the released birds do not undertake migrations. More recently, the population in all three major population regions have shown sustained growth over the past thirty-year period. Data from the US Fish and Wildlife Service^[20] show 400% growth in that period, with signs of increasing growth rates over time.

One impediment to the growth of the Trumpeter Swan population around the Great Lakes is the presence of a growing non-migratory Mute Swan population who compete for habitat.^[4][21]

The Ontario Trumpeter Swan Restoration Group started a conservation project in 1982, using eggs collected in the wild. Live birds have also been taken from the wild. Since then, 584 birds have been released in Ontario. Despite lead poisoning in the wild from shotgun pellets, the prospects for restoration are considered good.^[22]

The Trumpeter Swan is listed as threatened in the state of Minnesota.^[23]

See also

• Grande Prairie 'Swan City'
• Ralph Edwards, a leading Canadian conservationist of trumpeter swans
• The Trumpet of the Swan, a 1970 children's novel by E. B. White.

References

A mated pair on a lake, Kenai National Wildlife Refuge, Alaska

An adult and three juvenile trumpeter swans on the ice on Woods Lake near Oyama, British Columbia

External links

Wikimedia Commons has media related to Cygnus buccinator.

• BirdLife Species Factsheet
• Trumpeter Swan – Cygnus buccinator – USGS Patuxent Bird Identification InfoCenter
• Trumpeter Swan Wildlife Notebook – Alaska Department of Fish and Game
• The only Trumpeter Swan at The Wolseley Centre – Wolseley Wildlife
• Trumpeter Swan videos, photos, and sounds on the Internet Bird Collection
• WSU Beachwatchers – "Winter Visitors Arrive Trumpeter Swans again feeding in the fields"