NEW YORK - With just 11 days of winter to go, the snow is in retreat. In parts of the Northeast, at least 2 inches of snow melted in just the past day.
As people start venturing out, they're being greeted by a sound they haven't heard for months: the singing of birds.
America's thrushes and waxwings and warblers have managed to survive the winter.
As the snow melts in New York's Central Park, the birds sing a song of spring.
Robert DeCandido known as Birding Bob, has a PhD in evolutionary ecology. He says birds were OK, even thought this winter was harsh.
"If there's enough food around, the cold weather doesn't bother the birds," said DeCandido. "It's when there's cold weather and little to no food when it's a problem for birds."
Small birds can lose up to 10 percent of their body weight each night, so they have to eat a lot dring the day.
Little has been known about how small birds survive the cold, until now. Researchers at the University of Oxford put microchips on more than 2,000 songbirds to see exactly how they spend their winter days.
What they found was every morning birds leave their nests and scout out food sources. But they don't immediately eat. Instead, they fast, staying light and nimble enough to avoid being someone else's lunch. Then in the late afternoon, the birds return to where they saw food and chow down.
DeCandido says birds that don't migrate south for the winter have ways of staying warm.
"Well, you can shiver, you can burn fat. The birds will do that as well. But they also have down coats. You know how we have down coats that are stuffed with feathers? They have their own down coats," he said.
And as for their singing, you weren't mistaken. Songbirds do go quiet in winter, saving their energy until these warmer days, when their thoughts turn from survival to love.