Protecting Natural Resources through Collaboration and the GLRI
(Feb. 7, 2019) Eurasian mute swans (Cygnus olor) were introduced in Michigan in the early 1900s to grace ponds in municipal parks and on private estates. But since their arrival the elegant mute swans have spread to the wild, becoming a rapidly reproducing invasive menace in Michigan and the Great Lakes ecosystem.
The feral population grew to an estimated 17,520 birds in 2013. That number, and the associated negative impacts to habitat, vegetation and native waterfowl was unacceptable to Michigan Department of Natural Resources wildlife managers.
In Michigan, a primary concern is their impact on state-listed threatened and endangered species, including trumpeter swans (Cygnus buccinator). In 2010, the MDNR population modeling developed long-term management goals of fewer than 2000 birds statewide by 2030.
The GLRI has provided the opportunity for managers, biologists and multiple state, federal, tribal and private stakeholders to address this widespread and expanding invasive species. Since 2011, Wildlife Services teams implementing cooperative integrated mute swan damage management plans have removed 9,728 mute swans from Michigan, and the population has declined in recent years to an estimated 8,133 birds; a 54 percent reduction from the peak observed in 2013. Continued management efforts have helped keep the population lower today and surveys demonstrate sustained reduction in population size post GLRI funding.
Mute swan management has expanded and diversified each year as private lakes and waterways have enrolled in the program. When lethal control is impractical due to safety concerns, nest destruction is recommended for local population control. During the 2018 breeding season 93 nests containing 562 eggs were destroyed with subsequent reports of reduced populations and conflicts. More significantly, in 2017 WS removed 847 mute swans from 17 locations where trumpeter swans were also present. MDNR biologists report some sites previously dominated by mute swans are now occupied by trumpeter swans--a noteworthy success in the native swans’ recovery program.
Future projects will prioritize sites where mute swans conflict with threatened, endangered or native species of animals or plants.
Continued mute swan management in Michigan and the Great lakes region is needed to ensure success of native trumpeter swan recovery, decrease competition with other native waterfowl, reduce wetland habitat degradation and conflicts with humans.
WS monitors over 150 sites throughout the state annually. To assist with future management decisions, WS, MDNR, and Michigan State University are collaborating on a five-year mute swan research project. The project is aimed at improved tracking of seasonal mute swan movements, better estimations of birth and death rates, and an enhanced understanding of the swans’ population growth potential in the Great Lakes region. This data and population will be used to better inform management strategies.