But after reports of dead and injured swans came pouring in, officials reversed the decision and allowed feeding to resume, said Lori Naumann, the DNR's nongame public information officer.
"The winter was more severe than we anticipated," she said. "They just wouldn't leave like we thought they would."
Many swans that are not used to finding their own food in the harsh Minnesota winter ended up crashing into power lines or getting lead poisoning from eating shot pellets left behind years ago by waterfowl hunters.
The Wildlife Rehabilitation Center of Minnesota in Roseville has taken in about 40 swans since fall, nearly twice as many as usual, executive director Phil Jenni said.
Staff members have repaired broken wings and pumped swans' stomachs to remove lead pellets. They also have had to force-feed the lead-poisoned swans daily, because they lose the urge to eat.
The increase in injuries could reflect the general rise in the swan population, but because more injuries than usual were caused by encounters with power lines, the halt in feeding was probably to blame, Jenni said. Swans weakened by hunger were especially injury-prone, he said.
Naumann said getting the state's swans, which number almost 3,000, to migrate is crucial for the species' overall success.
When a large group of swans flock at one body of water, as they now do near the power plant in Monticello, the risk of disease drastically increases, Naumann said.
"Wildlife officials have been worried about this for years," she said. "It could essentially wipe out the whole population in one shot."
Wildlife officials plan to "go back to the drawing board" to find more effective ways to push swans into migration, Naumann said.
But cutting off their food supply probably isn't enough to get them to successfully migrate, said University of Minnesota fisheries and wildlife Prof. David Andersen.
Like many large waterfowl, swans don't know how to migrate instinctively; they have to be taught, Andersen said.
In Wisconsin, wildlife officials have used ultra-light aircraft to lead whooping cranes -- which, like swans, don't know how to navigate south instinctively -- on migration routes, Andersen said.
"Unless there are birds there that already know how to migrate, they're not going to be very successful," he said.
About 1,000 swans winter in Monticello and, with the help of donations to buy corn, bird lover Sheila Lawrence feeds them all. It's something she has been doing for 22 years.
Lawrence was relieved when wildlife officials lifted the feeding ban. "There's nothing like seeing a bird fly in with an 8-foot wingspan," she said. "Their wings are like angel wings."
Alex Robinson is a University of Minnesota student on assignment for the Star Tribune.