Trumpeter swan
The trumpeter swan is a species of swan found in North America. The heaviest living bird native to North America, it is also the largest extant species of waterfowl with a wingspan of 185 to 250 cm. 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. By 1933, fewer than 70 wild trumpeters were known to exist, and extinction seemed imminent, until aerial surveys discovered a Pacific population of several thousand trumpeters around Alaska's Copper River. Careful reintroductions by wildlife agencies and the Trumpeter Swan Society gradually restored the North American wild population to over 46,000 birds by 2010.
Description
The trumpeter swan is the largest extant species of waterfowl. Adults usually measure long, though large males can exceed in total length. The weight of adult birds is typically. Possibly due to seasonal variation based on food access and variability due to age, average weights in males have been reported to range from and from in females. It is one of the heaviest living birds or animals capable of flight. Alongside the mute swan, Dalmatian pelican, kori bustard, and Andean condor, it is one of a handful to weigh in excess of between the sexes, and one survey of wintering trumpeters found it averaged second only to the condor in mean mass. The trumpeter swan's wingspan ranges from, with the wing chord measuring. The largest known male trumpeter attained a length of, a wingspan of and a weight of. It is the second heaviest wild waterfowl ever found, as one mute swan was found to weigh a massive, but it was unclear whether the latter swan was still capable of flight because of its bulk.The adult trumpeter swan's plumage is entirely white. Like mute swan cygnets, the cygnets of the trumpeter swan have light grey plumage and pinkish legs, gaining their white plumage after about a year. As with the 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, is up to twice the length of a Canada goose's 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.
The mute swan, introduced to North America, is scarcely smaller. However, it can easily be distinguished by its orange bill and different physical structure. 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. The tundra swan 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. 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. Distinguishing tundra and trumpeter swans from a distance can be challenging without direct comparison but it is possible thanks to the trumpeter's obviously longer neck and larger, wedge-shaped bill as compared to the tundra swan.
Trumpeter swans have similar calls to whooper swans and Bewick's swans. They are loud and somewhat musical creatures, with their cry sounding similar to a trumpet, which gave the bird its name.
Range and habitat
Beginning in 1968, repeated in 1975, and then conducted at 5-year intervals, a cooperative continental survey of trumpeter swans was last conducted in 2015. The survey assesses trumpeter swan abundance and productivity throughout the entire breeding ranges of the three recognized North American populations: the Pacific Coast, Rocky Mountain, and Interior populations. From 1968 to 2010 the population has increased from 3,722 to approximately 46,225 birds, in large part due to re-introductions to its historic range.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. 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; they have even been observed as far south as Pagosa Springs, Colorado. Historically, they ranged as far south as Texas and southern California. In addition, there is a specimen in the Museum of Comparative Zoology in Cambridge, Massachuetts, that was shot by F. B. Armstrong in 1909 at Matamoros, Tamaulipas, Mexico. Since 1992, trumpeter swans have been found in Arkansas each November – February on Magness Lake outside of Heber Springs. In early 2017, a juvenile trumpeter swan took up residence in the French Broad River in Asheville, North Carolina, marking the first such sighting in that part of the state.
Non-migratory trumpeter swans have also been artificially introduced to some areas of Oregon, where they never originally occurred. Because of their natural beauty, they are suitable water fowl to attract bird watchers and other wildlife enthusiasts. Introductions of non-indigenous species in the Western states, for example through the Oregon Trumpeter Swan Program, have also been met with criticism, but generally the perceived attractiveness of natural sites has priority over the original range of any given species.
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. The young initially include insects, small fish, fish eggs and small crustaceans in their diet, providing additional protein, and change to a vegetation-based diet over the first few months.Breeding
Like other swans, 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. 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. The nest consists of a large, open bowl of grasses, sedges and various aquatic vegetation and have ranged in diameter from, the latter after repeated uses. The eggs average wide, long, and weigh about. 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, which attains similar average adult weights, and more than twice as heavy as those of kori bustards. 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. While nesting, trumpeter swans are territorial and harass other animals, including conspecifics, who enter the area of their nest.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 have 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, with the survival rate usually being 80–100% annually, unless they are hunted by humans. Predators of trumpeter swan eggs include common raven, common raccoon, wolverine, American black bear, brown bear, coyote, wolves, mountain lions, and northern river otter. 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, California gull, great horned owl, red fox and American mink. Larger cygnets and, rarely, nesting adults may be ambushed by golden eagle, bobcat, and probably both coyotes and gray wolves. 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 biting with their large bills; adults have managed to kill predators equal to their own weight in confrontations. Predation of adults when they are not nesting is rare; they may possibly be hunted by golden and bald eagles, but substantiated cases are few. Photos of an exceptional attack by a bald eagle on adult trumpeter swan in flight were taken in 2008, although the swan survived the predation attempt.Conservation status
Near extinction and rediscovery in Alaska
In the 19th and early 20th centuries, the trumpeter swan was hunted heavily, for game or meat, for the soft swanskins used in powder puffs, and for their quills and feathers. This species is also unusually sensitive to lead poisoning from ingesting lead shot while young. The Hudson's Bay Company captured thousands of swans annually with a total of 17,671 swans killed between 1853 and 1877. In 1908 Edward Preble wrote of the decline in the hunt with the number sold annually dropping from 1,312 in 1854 to 122 in 1877. Sir John Richardson wrote in 1831 that the trumpeter "is the most common Swan in the interior of the fur-counties... It is to the trumpeter that the bulk of the Swan-skins imported by the Hudson's Bay Company belong." By the early twentieth century breeding trumpeter swans were nearly extirpated in the United States, with a remnant population of fewer than 70 wild trumpeters in remote hot springs in or near Yellowstone National Park. Surprising news came from a 1950s aerial survey of Alaska's Copper River when several thousand trumpeters were discovered. This population provided critical genetic stock to complement the tri-state population for re-introductions in other parts of the swan's historic range.Historical range
In 1918 Joseph Grinnell wrote that trumpeter swans 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. In 1960 Winston E. Banko also placed their breeding range as far south as Nebraska, Missouri, Illinois, northwestern Indiana, but in Michigan turned this line northwards, placing a hypothetical eastern boundary up through Ontario to western Quebec and the eastern shore of James Bay. In 1984, Harry G. Lumsden posited that trumpeter swans may have been extirpated from eastern Canada by native people armed with firearms prior to the arrival of European explorers and noted archaeological remains of trumpeter swans as far east as Port au Choix, Newfoundland dating to 2,000 BCE. He cited historical observer records of what must have been breeding trumpeters, such as Father Hennepin's August report of swans on the Detroit River from Lake St. Clair to Lake Erie in 1679 and Antoine de la Mothe Cadillac's 1701 report of summering swans in the same area: "There are such large numbers of swans that the rushes among which they are massed might be taken for lilies." In the eastern United States the breeding range is potentially extended to North Carolina by the detailed report of John Lawson that "Of the swans we have two sorts, the one we call Trompeters...These are the largest sort we have...when spring comes on they go the Lakes to breed" versus "The sort of Swans called Hoopers; are the least."Reintroduction
Early efforts to reintroduce this bird into other parts of its original range, and to introduce it elsewhere, have had 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 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-native Eurasian mute swan population who compete for habitat.