Mute Swans - Invading Michigan's Waters
Table of Contents
- Why are Mute Swans a Problem?
- How To Tell a Mute Swan from a Native Swan
- What is the DNR Doing?
- How Can I Remove Mute Swans on My Property?
Mute swans are not native to Michigan, or to North America. They were brought to this country from Europe. Mute swans were introduced to this continent in the mid-1800s to adorn city parks and large estates. It is widely thought that all North American mute swan populations originated from the release or escape of individuals from these early captive flocks.
The first pair of feral mute swans was introduced to Michigan in 1919 in Charlevoix County. The population has continued to grow since that time. By the mid-1940s, the flock had increased to about 47 individuals. These swans spread through northern lower Michigan. In 1972, the flock near Traverse City numbered between 450-500 birds and was increasing at 15-22 percent annually. The population in northern lower Michigan was over 1,000 birds by 1982, with over 2,000 birds statewide by 1990. During this time, a southern flock of mute swans was also established in southwest Michigan.
Concerns over the expanding population of non-native mute swans were first expressed by the DNR in the 1960s, and that concern continues today. Mute swan management activities have been taking place for decades at varying levels.
Mute swan populations have the potential to increase rapidly if unchecked. Mute swans are relatively long-lived, contributing to their population growth. One study estimated mean annual death rate of young mute swans in Michigan ranged from 12-16 percent a year. From ages 4-8 years, annual mortality decreased to 2-7 percent per year. At age five, annual mortality averaged only two percent. Although essentially non-migratory, survival rates remain high through winter because the swans move to warm water discharges and rivers. By 2000, the statewide breeding population was estimated to be about 5,700. In just ten years, that number rose to over 15,500. The DNR estimates approximately an increase of about 9-10 percent each year. Interestingly, Michigan now has the highest population of mute swans in North America.
With growing concern over burgeoning mute swan numbers, the DNR set a long-term goal to reduce the statewide mute swan population to less than 2,000 by the year 2030.
The mute swan population in Michigan is tracked twice yearly by the DNR. First, during a mid-winter waterfowl count conducted in early-January, then by the Michigan Spring Breeding Waterfowl Survey conducted each April-May. Mute swan population estimates are derived each year using data from the Spring Breeding Waterfowl Survey. This is an established aerial survey that the DNR has participated in since 1991. Flights are conducted at low elevation, slow speeds and follow the same transect routes each year. The survey methodology used is scientifically sound and proven and used by other states and Canadian provinces.
There are three primary issues with mute swans: threat to humans, danger to native wildlife and destruction of wetland habitat.
- THREAT TO HUMANS
Mute swans are large, conspicuous birds and have little fear of humans. They are easily observed by the public and offer a chance for people to come in close contact with wildlife. Each year, the DNR gets reports of mute swan attacks on people in watercraft and on shore. These situations all pose potentially dangerous results, and as the mute swan population grows, so do the conflicts.
Nesting swans can be very aggressive to humans who come too close to their territory. Mute swans will attack humans, especially small children, who get too close to their nest or young. Canoeists, kayakers and those operating personal watercraft have also been attacked when too close to mute swan territories. Mute swans are aggressive and may pose a danger to humans and can, in certain situations, effect human use of property when humans are excluded from nesting areas by swans defending their territories.
- DANGER TO NATIVE WILDLIFE
Mute swans are one of the world's most aggressive waterfowl species, especially during nesting and brood-rearing. Mute swans exhibit aggression toward other waterfowl and can displace native waterfowl from their nesting and feeding areas by attacking, injuring and even killing other birds.
In Michigan, of particular concern are native breeding waterfowl and water birds such as trumpeter swans (state threatened), Canada geese, ducks, common loons (state threatened), and black terns (state special concern).
The trumpeter swan is native to Michigan, and is on our state's threatened species list. It has been on the road to recovery; however, the increasing presence of the invasive mute swan is threatening the breeding success of this native bird. To ensure the protection of the trumpeter swan, the mute swan population must be drastically reduced.
Mute swan displacement and aggression toward native wildlife occurs frequently throughout North America. For example, the New York State Department of Environmental Conservation reported that three pairs of captive mute swans killed at least 50 ducks and geese in a zoo. The Maryland Department of Natural Resources has reported records of mute swans killing mallard ducklings, Canada goose goslings and cygnets of other mute swans. Not just waterfowl species are at risk. For example, a large molting flock of Maryland mute swans caused a colony of least terns and black skimmers to abandon their nesting colony by trampling nests containing eggs and chicks. These swans also displaced nesting Forster's and common terns.
- DESTRUCTION OF WETLAND HABITAT
Mute swans feed primarily on water plants (e.g., pondweed, coontail, waterweed, wild rice and wild celery). By feeding heavily on this food source, mute swans reduce the availability of these plants to native wildlife, and may ultimately reduce the carrying capacity of wetlands for native wildlife species. Adult mute swans consume big quantities of these plants (about 4-8 pounds per swan per day) and often uproot more plants than they actually consume. As mute swans occupy habitat year-round in many locations, there is potential for depletion of this aquatic vegetation by continuous feeding.
The wetland plants that mute swans are removing play an important role in aquatic ecosystems by providing both food and cover to a variety of vertebrate and invertebrate species. Many wildlife and fish species feed on animals that live in these plants. Wildlife biologists have concern over the declining numbers of native duck species such as canvasbacks and scaup. These diving ducks feed on particular aquatic plants and are negatively impacted when mute swans reduce or eliminate this food source.
The most notable difference between mute swans and the two native swan species found in Michigan (trumpeter swan and tundra swan) is that adult mute swans have orange bills. The two native swans have black bills. Mute swans also have a black knob on the top of their bill, which is absent in the native swan species. Mute swans typically have an "S"-shaped curve to their neck, while trumpeter swans have a "C"-shaped curve. Mute swans are also generally quieter than trumpeter swans, which have a loud trumpet-like call.
image courtesy of the Trumpeter Swan Society
The DNR's Mute Swan Management and Control Program Policy and Procedures outlines both short- and long-term population goals for mute swans in Michigan. The short-term goal is to reduce the statewide mute swan population growth to zero by 2016. A longer-term goal is to reduce Michigan's mute swan population to less than 2,000 by 2030.
There are many conservation groups that support the DNR's drastic reduction of mute swan numbers because of the negative impacts mute swan have on native birds and wetland habitat. National Audubon Society, Michigan Audubon Society, the American Bird Conservancy and Ducks Unlimited are just a few organizations that have endorsed the reduction of mute swan populations.
Though hunting mute swans is not allowed, the DNR issues permits to remove mute swans and/or their nests and eggs.
Mute swans are not federally protected. Federal protection was removed by the Migratory Bird Treaty Reform Act in 2004 because mute swans are not native to the United States. Therefore, the regulation of mute swans is the exclusive jurisdiction of the state, and mute swans are protected under Michigan law. The DNR allows the removal of mute swans and their nests and eggs under permit for any of the following situations:
- To stabilize or reduce mute swan population levels or to prevent new populations of feral mute swans from being established.
- To prevent mute swan interference with the establishment, re-establishment or reproductive success of endangered, threatened or native wildlife species; and with the establishment or re-establishment of native vegetation.
- To protect public health, safety, or welfare.
Permits are required to take mute swans or their nests and eggs.
If you have mute swans on your property and wish to remove them or their nests and eggs, you must request a permit from your local DNR office.
See a list of DNR offices or call 517-284-9453.
If you have multiple landowners on your water body, you must submit a petition signed by 70 percent of the lakeshore owners or 70 percent of the shoreline ownership; or provide a resolution from an elected local government official (township, city, etc.) who represents the property owners on the body of water that approves mute swan control for that site.
Permittees can be authorized to conduct control activities themselves or contract a licensed nuisance animal control firm. If permittees choose to conduct control activities themselves, DNR staff must oversee mute swan removal the first year. Permittees must follow safety protocols and notification procedures. USDA-Wildlife Services has received invasive species grant funding in recent years for mute swan removal and is authorized to conduct control activities on both private and public land. Your local DNR biologist can inform you if your site may be able to benefit from these special grant funds.
For more details on permitting procedures, see Michigan Mute Swan Control and Management Policy and Procedures.
You and your neighbors can help protect Michigan's natural resources by controlling invasive mute swans on your lakes and wetlands.