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 a species of swan found in North America. The heaviest living bird native to North America, it also is on average, the largest extant species of waterfowl.[2] It is the 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 (4 ft 6 in–5 ft 5 in) long, though large males can exceed 180 cm (71 in) in total length.[2][4][5][6] The weight of adult birds is typically 7–13.6 kg (15–30 lb). Possible due to seasonal variation based on food access and variability due to age, average weights in males have been reported to range from 10.9 to 12.7 kg (24 to 28 lb) and from 9.4 to 10.3 kg (21 to 23 lb) in females.[2][7][8][9] It is one of the heaviest living birds or animals capable of flight. Alongside the mute swan (Cygnus olor), Dalmatian pelican (Pelecanus crispus) and Andean condor (Vultur gryphus) and the kori bustard (Ardeotis kori), it is one of the handful to scale in excess of 10 kg (22 lb) between the sexes and one survey of wintering trumpeters found it averaged second only to the condor in mean mass.[10][11] The trumpeter swan's wingspan ranges from 185 to 250 cm (6 ft 1 in to 8 ft 2 in), with the wing chord measuring 60–68 cm (24–27 in).[2][4][5][12] The largest known male trumpeter attained a length of 183 cm (72 in), a wingspan of 3.1 m (10 ft 2 in) and a weight of 17.2 kg (38 lb). It is the second heaviest wild waterfowl ever found, as one mute swan was found to weigh a massive 23 kg (51 lb), but it has been stated that was unclear whether this swan was still capable of flight due to its bulk.[13]

The adult trumpeter swan is all white in plumage. As with a whooper swan, this species has upright posture and generally swims with a straight neck. 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, measuring 10.5–12 cm (4.1–4.7 in), is up to twice the length of a Canada Goose's (Branta canadensis) bill and is the largest of any waterfowl. 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, 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 year-around in developed areas near human habitation in North America, whereas Trumpeters are usually only found in pristine wetlands with minimal human disturbance, especially while breeding.[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.[14] Distinguishing tundra and trumpeter swans from a distance (when size is harder to gauge) can be challenging without direct comparison but it is possible thanks to the trumpeter's obviously longer neck (the great length of which is apparent even when the swan is not standing or swimming upright) and larger, wedge-shaped bill as compared to the tundra swan.

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.[15] 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;[16] they have even been observed as far south as Pagosa Springs, Colorado. Historically, they range as far south as Texas and southern California.[17] Since 1992, trumpeter swans have been found in Arkansas each November – February on Magness Lake outside of Heber Springs.[18]

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.[19] The young feed 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 5 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.[15] 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.[15] 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.[20] The eggs average 73 millimetres (2.9 in) wide, 113.5 millimetres (4.5 in) long, and weigh about 320 grams (11.3 oz).[15] The eggs are quite possibly the largest of any flying bird alive today, in comparison they are about 20% larger in dimensions and mass than those of an Andean condor (Vultur gryphus), which attains similar average adult weights, and more than twice as heavy as those of kori bustards (Ardeotis kori).[21][22][23] The incubation period is 32 to 37 days, handled 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.[24] While nesting, trumpeter swans are territorial and harass other animals, including conspecifics, who enter the area of their nest.[15]

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, members of this species has survived to 33 years old and, in the wild, have 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.[25] 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.[26] 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.[27]

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.[17] The trumpeter was rare or extinct in most of the United States by the early twentieth century.[17] 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[28] 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][29]

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.[30]

The trumpeter swan is listed as threatened in the state of Minnesota.[31]

See also

References

A mated pair on a lake, Kenai National Wildlife Refuge, Alaska
An adult and three juvenile trumpeter swans on the shore of Woods Lake, near Oyama, British Columbia

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  1. ↑ BirdLife International (2012). "Cygnus buccinator". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Madge, Steve; Burn, Hilary (1988). Waterfowl: An Identification Guide to the Ducks, Geese, and Swans of the World. Boston: Houghton Mifflin. ISBN 0-395-46727-6.
  3. ↑ Morony, J. J., Jr.; Bock, W. J.; Farrand, J., Jr. (1975). Reference list of the birds of the world. New York: American Museum of Natural History. OCLC 483451163.
  4. ↑ 4.0 4.1 4.2 "Mute Swan". Cornell Lab of Ornithology. Retrieved 2011-12-18.
  5. ↑ 5.0 5.1 Ogilvie, M. A.; Young, S. (2004). Wildfowl of the World. New Holland Publishers. ISBN 978-1-84330-328-2.
  6. ↑ "Trumpeter Swan, Life History". All About Birds. Cornell Lab of Orinthology. Retrieved 2012-06-22.
  7. ↑ Drewien, R. C., & Bouffard, S. H. (1994). Winter body mass and measurements of Trumpeter Swans Cygnus buccinator. Wildfowl, 45(45), 22-32.
  8. ↑ Sparling, D. W., Day, D., & Klein, P. (1999). Acute toxicity and sublethal effects of white phosphorus in mute swans, Cygnus olor. Archives of environmental contamination and toxicology, 36(3), 316-322.
  9. ↑ James, M. L. (2000). Status of the trumpeter swan (Cygnus buccinator) in Alberta. Alberta Environment, Fisheries & Wildlife Management Division, Resource Status and Assessment Branch.
  10. ↑ CRC Handbook of Avian Body Masses, 2nd Edition by John B. Dunning Jr. (Editor). CRC Press (2008), ISBN 978-1-4200-6444-5.
  11. ↑ Greenwood, J. J., Gregory, R. D., Harris, S., Morris, P. A., & Yalden, D. W. (1996). Relations between abundance, body size and species number in British birds and mammals. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 351(1337), 265-278.
  12. ↑ "Trumpeter Swan video, photos and facts". Arkive: Images of Life on Earth. Retrieved 2012-06-21.
  13. ↑ Wood, Gerald (1983). The Guinness Book of Animal Facts and Feats. ISBN 978-0-85112-235-9.
  14. ↑ Sibley, David. "Trumpeter Swans with yellow loral spots". Retrieved 13 December 2011.
  15. ↑ 15.0 15.1 15.2 15.3 15.4 Mitchell, C. D.; Eichholz, M. W. (2010). "Trumpeter swan (Cygnus buccinator)". In Poole, A. The Birds of North America Online. Ithaca: Cornell Lab of Ornithology.
  16. ↑ "''...Trumpeter Swans...''". Washington State University Beach Watchers. Retrieved 2011-12-18.
  17. ↑ 17.0 17.1 17.2 Grinnell, Joseph; Bryant, Harold Child; Storer, Tracy Irwin (1918). The Game Birds of California. University of California Press. p. 254. Retrieved 2010-08-18.
  18. ↑ Galiano, Amanda. "Trumpeter Swans on Magness Lake – Heber Springs". Retrieved 2012-08-14.
  19. ↑ Squires, J. R.; Anderson, S.H. (1997). "Changes in trumpeter swan (Cygnus buccinator) activities from winter to spring in the greater Yellowstone area". American Midland Naturalist 138 (1): 208–214. doi:10.2307/2426667. JSTOR 2426667.
  20. ↑ Slater, G. (2006). "'Trumpeter Swan (Cygnus buccinator): a technical conservation assessment". U.S. Forest Service.
  21. ↑ Rohwer, F. C.; Eisenhauer, D. I. (1989). "Egg mass and clutch size relationships in geese, eiders, and swans". Ornis Scandinavica: 43–48.
  22. ↑ Brown, L.; Amadon, D. (1968). Eagles, hawks and falcons of the world. New York: McGraw-Hill.
  23. ↑ Ginn, P. J.; McIlleron, W.G.; Milstein, P. le S. (1989). The Complete Book of southern African birds. Cape Town: Struik Winchester. ISBN 9780947430115.
  24. ↑ "Trumpeter Swan Fact Sheet". Lincoln Park Zoo. Retrieved 2011-12-18.
  25. ↑ Krementz, D.; Barker, R.; Nichols, J. (1997). "Sources of Variation in Waterfowl Survival Rates". The Auk 114 (2): 93–102. JSTOR 4089068.
  26. ↑ Kraft, F. (1946). "The Flying Behemoth is Coming Back". Saturday Evening Post 219 (6). p. 6.
  27. ↑ "Bald Eagle attacking a Trumpter Swan". Utahbirds.org. Retrieved 2012-08-21.
  28. ↑ Caithamer, David F. (February 2001). "Trumpeter Swan Population Status, 2000" (PDF). U.S. Fish and Wildlife Service. Retrieved 2011-12-18.
  29. ↑ "Trumpeter Swan". Hinterland Who's Who. Environment Canada & Canadian Wildlife Federation. Archived from the original on 2011-07-22.
  30. ↑ "Toronto Zoo > Conservation > Birds". Retrieved 2009-09-22.
  31. ↑ "Minnesota Endangered & Threatened Species List" (PDF). Retrieved 2011-12-18.

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