For the first time since 1966 trumpeter swan cygnets have fledged from Swan Lake, in northern Yellowstone National Park.
Four cygnets hatched at the lake about four months ago, according to the park's staff. It takes only about 1.5 days for the newly born cygnets to leave the nest and follow their parents into the water to begin feeding.
At first, they can only dabble and graze, then as time passes, they learn to forage and care for themselves while staying close together as a family group.
About three to four months after birth, they begin to fly making short trips around the area.
Of the four cygnets that were born on Swan Lake, one took a little longer to develop the ability to fly, creating an interesting situation. It could not sustain flight with the rest of the cygnets and was left behind when the lake started to freeze over.
Sometimes when a cygnet is not able to fly before freeze-up in autumn, it will die. In this case, the weather warmed up and the lone cygnet was able to forage on its own in the lake. And, interestingly enough, in about a week and a half, the family returned and reunited with the young swan.
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The fourth cygnet was finally able to fly, and earlier this month they all left together to find open water.
Although they once nested from Alaska to northern Missouri, trumpeter swans were nearly extirpated in the lower 48 states by 1930 due to habitat loss and hunting. A small population of about 70 birds survived in the Greater Yellowstone Ecosystem. With intensive management, this population provided the basis for widespread swan recovery later in the century.
As a result of conservation measures, populations across the continental United States began increasing. As of 2015, there are about 63,000 trumpeter swans in North America belonging to three distinct subpopulations: the Pacific, the Rocky Mountain, and the Interior.
Swan numbers in the Greater Yellowstone Ecosystem, belonging to the Rocky Mountain subpopulation, grew steadily through the early 1960s, after which cygnet production in Yellowstone and subsequent recruitment of adults into the breeding population began declining after the Red Rock Lakes National Wildlife Refuge feeding program ended and winter ponds were drained in the early 1990s.
Other factors contributing to the decline may include predation, climate change and human disturbance. In 2019, park biologists observed 27 trumpeter swans in Yellowstone, including 21 adults and six cygnets. Two pairs attempted to nest in the park, on Swan Lake and an unnamed pond west of Lilypad Lake in the Bechler region, and a third pair on Grebe Lake did not nest in 2019.
A fourth pair attempted to nest on Junco Lake, outside the park’s southern boundary. Both nest attempts in the park were successful, hatching at least seven cygnets and fledging four.
Four young trumpeter swans were released in Yellowstone in 2019 in Hayden Valley on the Yellowstone River, near the confluence with Alum Creek. Staff hope that these released swans will become bonded to their release location and return the following spring. In total, the park has released 35 cygnets over a seven-year period. Although several individuals are frequently seen within the park boundaries during the breeding season, none of the released cygnets have nested within the park yet.
Swans typically take at least four years to reach sexual maturity, so biologists are hopeful these young birds may breed in coming years. The release program is part of an ongoing effort to augment Yellowstone’s swan populations and increase the number of breeding pairs that nest inside the park.
Nearly all Rocky Mountain trumpeter swans — including several thousand that migrate from Canada — winter in ice-free waters in the Greater Yellowstone Ecosystem, but only a portion of them remain here to breed.