As the sun rises over the Mississippi River near Brownsville, Minn., thousands of migrating tundra swans call out to one another, flap their wings, or fly low over the water. Silhouetted against the sky across the river, the birds flock in groups of anywhere from three or four to 60 or more.
These birds leave the arctic to make a 3,000-mile trek to their winter grounds on the East Coast. The annual journey requires fuel, and lots of it. They eat roughly half their body weight per day — about six pounds worth.
"They go where the food is," says Hallie Rasmussen, visitor services manager for Upper Mississippi National Wildlife and Fish Refuge. "It's like a buffet out there for them."
Their time in Minnesota is short. The swans came in this past week and as soon as the water starts to freeze, they will leave. That could be as soon as next week.