Mute Swans
Mute swans (Cygnus color) are so named due to the fact that they are typically less vocal than other swan species. They can be readily identified by their orange bills and curved necks. The single visible difference between males and females is the black bulb at the base of the upper bill. It is larger in males, particularly during the breeding season. Mute swans are one of the heaviest flying birds with males in the wild reaching up to 30 pounds. Mature mutes can have a wingspan up to nearly eight feet.
Nests are typically on mounds built near the water at isolated locations. They are used for multiple years. At Indian Lake, mute swans have used nesting sites on ‘Bird Island’ and Cedar Point. The female lays 4-10 eggs over successive days and then broods them for 36 days. Once hatched, the cygnets can swim in a few days but require 4-5 months before they can fly.
Mute swans are considered to be one of the most aggressive bird species in the world. They are particularly aggressive in defense of their nests and the cygnets. The aggressive behavior starts with loud hissing, then striking using the spurs on the wings or biting. They will attack canoes, personal watercraft, and people. Mute swans often display aggression toward other swans, loons, geese, and ducks. Their strong territorial behavior often results in small lakes having only a single pair. This has been the situation at Indian Lake the last few years as the very aggressive male has driven off both mute and trumpeter swans.
Mute swans are considered an invasive species. They are not native to North America, having been imported in the mid 1800’s. They were brought to Michigan in 1917. Escapees produced an expanding feral population that has resulted in a number of issues. As stated above, the aggressive behavior has resulted in the extirpating of other aquatic bird species as well as conflicts with humans. According to the USDA, mute swans fed by people become more aggressive in seeking food. In some locations where mute swans congregate, they also uproot large amounts of aquatic vegetation that is habitat for native wetland birds, fish, and invertebrates. Feces have been shown to transmit swimmers itch, salmonellosis, and E. coli.
In order to minimize the negative impacts of mute swans, the Michigan DNR has a policy of reducing the mute swan population and eliminating them from state lands. The population has been reduced from an estimated 15,500 mutes in 2010 to around 8,000 in 2018. Because mute swans are an invasive species, they are no longer protected by the federal Migratory Bird Treaty Act. However, Michigan does regulate actions that can be used to reduce the population size. Organizations can obtain permits to conduct egg and nest destruction similar to that used on nuisance geese. Authorized persons are also allowed to remove mute swans. These birds can only be euthanized.
Trumpeter Swans
Trumpeter swans (Cygnus buccinator) are given their name because of their musical calls similar to a trumpet. In contrast to the mute swans, the trumpeters have a black bill and swim with a straight neck. They are usually slightly larger than the mutes being the largest bird in North America. Typically, they weigh 21-30 pounds with a 6-8 foot wingspan.
Trumpeter swans were once eliminated from Michigan and were nearly extinct. In 1933, there were less than 70 known in the wild. Fortunately, a population of several thousand was discovered in Alaska. These birds were used in the recovery efforts that resulted in a population of more than 46,000 by 2010. Trumpeters were reintroduced to Michigan in 1986. By 2015, the population had increased to more than 56. Trumpeters have been seen occasionally on Indian Lake over the last several years. One pair attempted to nest in 2022 but were chased off the lake by the mute swans.
Like mute swans, trumpeters reuse their large nests found near the water. Pairing is reported to occur anywhere from 3-7 years of age. Clutch size is 4-6 eggs. The parents can be aggressive when protecting the eggs or cygnets. Their protective behavior starts with head bobbing and later with hissing.
Trumpeters diet is similar to mutes but there is a lack of information whether or not trumpeters tear up the vegetation like the mutes. They may or may not migrate. Some sources say that introduced populations tend not to migrate while another states that trumpeters from Michigan migrate to waters near the Mississippi River in Arkansas and Missouri or even west to Oklahoma.
In interactions between mute and trumpeter swans, the highly aggressive mutes out compete and drive out the trumpeter swans. This has been observed at Indian Lake and other locations. Along Lake Erie, the introduced trumpeter population had a substantial increase only after the removal of mute swans. It is likely that trumpeter swans will not be established on Indian Lake without removing the mute swans. However, mute swan removal will not guarantee establishment of a trumpeter population since they prefer areas without significant human disturbance.
Trumpeter swans on Indian Lake in April, 2022. Photo courtesy of Tom McPherson.
Literature Used:
Great Lakes Restoration: https://www.glri.us/
Indians DNR: https://www.in.gov/dnr/
Michigan DNR: https://www.michigan.gov/dnr
Minnesota DNR: https://www.dnr.state.mn.us/
New York Department of Environmental Conservation: https://www.dec.ny.gov/
United States Department of Agriculture: https://www.usda.gov/
United States Fish and Wildlife Service: https://www.fws.gov/
Wikipedia: https://en.wikipedia.org