ROSEVILLE, Minn. (AP) -

This year's deep snow and extreme cold have taken a toll on Minnesota wildlife -- especially swans and other waterfowl that can't find open water on the state's many frozen lakes.

Minnesota Public Radio News reports that the Wildlife Rehabilitation Center of Minnesota is treating about a half dozen birds that have been coming in with injuries.

Veterinarian Agnes Hutchinson says when they can't find open water, swans and other birds have to stand on ice more than usual, and that's hard on their feet.

Center director Phil Jenni says birds are also starving because they can't find a food source on land. And, when there is no open water, birds are also more vulnerable to attack from raptors and other predators.