“The main concerns are the problems with populations with native species,” said Nik Kalejs, wildlife habitat biologist at the Muskegon State Game Area. “They’re an aggressive, territorial bird — and because of their size, they’re good at excluding other native birds.”
The mute swan is a threat to the native trumpeter swan, a threatened species in Michigan. The mute swan is noted for its white, billowy feathers; black mask-like marking; orange bill; and long, curved neck.
Mute swans are not native to Michigan or even to North America. They were brought from Europe 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.
Kalejs said the mute swan has a detrimental impact on wetland ecology, as they consume a lot of biomass and take up large swaths of land.
State officials claim mute swans are invasive because they are non-native species that have become established and spread rapidly, causing negative impacts such as competition with native wildlife, displacement of native species and degradation of wetland habitat.
While they are aggressive, Kalejs said the main concern lies in their interaction with other waterfowl.
“The larger issue in the long run is the issue of a non-native species outcompeting a native bird,” he said.
Ottawa County park officials say they are keeping an eye on county lands to make sure the mute swan doesn’t become an issue.
“Fortunately, we haven’t had to address that on our property yet,” said Melanie Manion, supervisor of the county's Natural Resources Management. “If we do see them as a problem, we’ll begin to address the pros and cons of addressing them.”
The county park system has a management system in place to detect and remove potential threats from invasive plants. It is being discussed if a similar strategy could be adopted for the birds.
“We want to get things early on before the cost of management is too high,” Manion said. “We think they’re beautiful, but they are creating significant harm.”
State wildlife experts say that they have been watching the mute swan population for decades.
“It’s more statewide,” said Barbara Avers of the Michigan Department of Natural Resources. “Every spring, we fly our breeding waterfowl survey.”
The flights are conducted to give estimates on bird populations. They are conducted at low elevation and slow speeds, and follow the same routes each year.
Both Avers and Kalejs noted that the mute swan population has been trending upward every year.
“Our recent estimate is 15,500 (mute swans),” Avers said. “We know that there were two in 1919. ... To stop that growth, we’ve been more aggressive in our control measures."
The state hopes to have fewer than 2,000 by 2030. To reach this goal, the DNR has been instituting some management efforts.
To read more of this story, see Saturday’s print or e-edition of the Grand Haven Tribune.