Will Carolina Wrens make it through this winter?

What's more important to a bird's survival? The ability to withstand cold weather or access to food? 

Matt Miller, a senior science writer at The Nature Conservancy, says Carolina Wrens are losing ground because of the polar vortex--that extremely cold air mass that has been sweeping down from the Arctic this winter.

Carolina Wren

Miller writes, "While visiting my parents and brother in central Pennsylvania over the holidays, I enjoyed watching the antics of the Carolina Wrens visiting their bird feeders. They're fun birds to observe, always active and vocal."

Carolina Wrens have been expanding their range northward over recent decades, he points out. "They are not migrants: they live in a locale year round."

"However," he writes, "these birds don't fare well during periods of very cold weather. Since they don't migrate, they often perish."

That pattern is consistent with results of the Great Backyard Bird Count, held each February, he says.

"The Carolina Wren population eventually expands northwards again," he adds, "It takes time. According to Great Backyard Bird Count reports, it can be 10 years or more until Carolina Wrens return to northern states in numbers following a cold weather die-off."

After the frigid weather set in, he called his parents; they told him they have not seen a Carolina Wren since.

Several of Miller's readers suggest that it's not extreme temperature that harms the wrens--it's lack of food.

Richard Gregson says his hometown of Montreal, Canada, has had temperatures of minus 13 degrees Fahrenheit yet the wrens survive.

Carolina Wrens, he says, "are adapted for finding food around their feet in the leaf litter of forest floors and when there is a deep, crusty snow they cannot feed … unless they find a secondary food source such as a well stocked garden feeder."

Another reader, Sally Chambliss, writes of a similar experience. The Carolina Wrens in her neighborhood in western Massachusetts "are doing well" in the extreme cold "because I feed them beef suet and sunflower seeds. They have been in my area for a few years and have had several successful births in one of my backyard birdhouses. Suet is very important to their survival."

You can read full Miller's account on the winter survival prospects of Carolina Wrens and other animal species by clicking here.

How can you help? Carolina Wrens eat suet which is high in calories to help keep warm. They will also peck at sunflower seeds with no shell.