JACKSON, Wyo. — Trumpeter swan numbers in Wyoming, Idaho and Montana have risen about 25 percent from a year ago thanks in part to the birds learning to find new food sources during the winter, a biologist says.
A recent survey of the swans counted an estimated 6,775 swans in the region this year, compared to some 5,370 counted in 2014.
Because of warm weather and abundant open water, the large white waterfowl were beginning to move north from wintering grounds about a month earlier than usual, Wyoming Game and Fish Department nongame biologist Susan Patla said.
“They’re using some of the shallow water ponds that tend to stay frozen and also some of the shallow areas along the rivers,” she said. “Some of the birds were … very close to or were on their nesting areas.”
Swans normally found wintering south of Afton in southwest Wyoming were as far north as Palisades Reservoir, Patla said.
Some trumpeter swans in the three-state area have learned new foraging strategies that have helped their numbers rise in the region, Patla told the Jackson Hole News & Guide.
“They spread out a lot more, and many of the swans in Idaho have now learned to field feed in winter,” she said. “There’s a lot of leftover potatoes in the fields, and they eat a lot of tubers. This is a behavior that’s developed fairly recently, over the last 15 years.”
By counting in the fall, winter, spring and summer, Patla is able to sort out how many migratory and resident swans there are and determine their breeding and nesting success.
The Canadian birds will begin to depart late this month and will be gone by mid-April, she said.