Yellowstone National Park may be well-known for its role in rebuilding populations of large mammals like grizzly bears, wolves and bison, yet trumpeter swans have a similar story of dogged recovery that is not as well known.
“They were reduced to only a few individuals and have made a big comeback, yet they are still struggling in Yellowstone and the Tetons,” Evan Shields, a Montana State University graduate student who is studying the birds, told The Billings Gazette.
The reasons for the decline of trumpeters in the park could include: an increase in tourists who may disturb nesting parents, leaving eggs vulnerable to predators; drought and climate change that has reduced the number or quality of wetlands and their food supply; and predation.
Although he had previously worked with compelling species like mountain lions and wolves in Yellowstone, Shields sees the swans as “awfully charismatic birds.” After all, they are big — weighing more than 20 pounds and with wings spanning 8 feet. That makes them the largest wild waterfowl on the continent. They can also live a long time, up to 25 years, and will mate for life.
In an attempt to understand why the birds are struggling to survive and reproduce in the park, since 2018 Shields has been talking to park scientists, collecting and collating existing data in search of answers. He hopes to publish his findings next spring.
On Sept. 19, staff from the park, Wyoming Wetlands Society and the Ricketts Conservation Foundation released eight young swans, called cygnets, at Alum Creek in the Hayden Valley. Such releases have taken place every year since 2012. Since then, more than 40 birds have been freed.
“This release is part of an ongoing restoration project to increase territorial pairs of swans which have undergone a decades-long decline in the park,” according to a park press release. “Researchers are collecting population data such as nest success, number of territorial pairs, and the number of cygnets produced each year. This data may help determine the reasons for the decline.
“Recent releases and other restoration efforts have bolstered the population to over 20 birds and five territorial pairs, including natural reproduction in some years,” the park’s staff said.
Similar cygnet releases have taken place in the Madison, Bitterroot and Blackfoot valleys in Montana, as well as the Jackson region in Wyoming.
The idea of releasing young birds is that they will imprint on the area and return to nest. Trumpeters won’t breed until they