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12
May

Trumpeter Swans and Montana’s Common Loon

By Elaine Caton, Swan Restoration Coordinator

Written for the Montana Loon Society‘s 2021 Newsletter

In 2005, the Blackfoot Challenge in partnership with the US Fish and Wildlife Service began an effort to restore Trumpeter Swans to the Blackfoot watershed. Since, we have released over 200 young captive-raised trumpeters in the Ovando-Helmville area, and have established 6-8 nesting pairs. The first nests were in the central part of the watershed near Ovando, but they have since expanded to the Lincoln area and Clearwater valley.

As trumpeters settle in lakes and wetlands they’ve been absent from for more than 100 years, they are also moving into territories occupied by loons, especially in the Clearwater. A pair of swans began nesting on Placid Lake in 2016, where a pair of loons already had a territory. Both swans and loons have nested there since, and except for the first nest attempt by the swans, both species have successfully hatched and raised young each year. In 2018, a Trumpeter Swan pair set up territory on Rainy Lake (which also has nesting loons) and nested in 2019. Both species were successful in 2019 and 2020, with their nests fairly close together on both lakes.

Swans and loons are known to be fiercely territorial and protective of their young. Both have similar habitat requirements for nest sites: undisturbed areas on islands or along the shore of lakes or wetlands, with aquatic vegetation to help conceal them and serve as nest-building material. Given these factors, these species could be antagonists and compete for habitat. However, although swans are known to drive geese out of their territories, swans and loons seem to coexist peacefully. This is likely due in part to the fact that they do not compete for food; swans are herbivores, and eat aquatic plants growing beneath the surface of the water, while loons eat fish and other aquatic animals. So unless one would closely approach the nest or young of the other species, they appear to largely ignore each other and may unintentionally help each other by sounding an alarm when potential predators are nearby, and even by driving predators away.

Swans and loons are known to nest in close proximity (as close as 25 feet apart) in other areas and loons may benefit from the swans aggressive defense of nests and young. Trumpeters can successfully defend their young from coyotes. In Alaska, a bush pilot even reported a pair of swans drive an Alaskan brown bear away from their nest! (Carroll Henderson, pers. comm.) Although loons can sometimes successfully repel aerial predators like eagles, their smaller size and awkward gait on land probably make it difficult for them to defend
against four-legged critters as successfully as swans.

Another shared aspect of loon and swan nesting is their sensitivity to human disturbance. Both tend to be very wary while incubating, and will generally leave the nest if people approach. This can give nest robbers like ravens an opportunity to steal eggs, or in cool, wet, or very warm weather can cause the eggs to perish if left too long. Having swans and loons nesting closely together allows those of us who monitor these two species (Blackfoot Challenge, Montana Fish, Wildlife, and Parks, and the US Fish and Wildlife Service and for loons, the MT Common Loon Working Group, and the Montana Loon Society) to combine efforts to keep an eye on both, and to take steps like putting
up signs around nests that protect both.

Canoeists keeping their distance from Trumpeter Swans on Rainy Lake. Photo by Helene Michael.

The many Montanans and visitors who enjoy seeing and hearing these rare birds are rewarded with the delightful opportunity to see families of both on our local lakes. Helene Michael of Seeley wrote after a visit to Rainy Lake, “Everyone camping and swimming are keeping their distance as the swans venture out around the lake… and we were treated to some loon activity and calling as well.”

Header photo: Trumpeter Swan family on Rainy Lake. Photo by Helene Michael.

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