Help Birds Weather Winter
Fatty foods and fluffy feathers benefit cold birds, but they still can use our help
AS TEMPERATURES DROP across much of the country, we don heavy jackets, hats and gloves to keep warm. But what about backyard birds? Like humans, birds are warm-blooded, yet they have higher metabolic rates and, therefore, higher body temperatures—105 degrees F on average. When the mercury dips, it can be tough to maintain that heat. Survival depends on both physical and behavioral adaptations.
Birds’ feathers provide remarkable insulation, and many species grow an extra layer of down as part of a late-fall molt. Feathers are aligned to create tiny air pockets, and their outer layer is coated with waterproofing oil produced by a gland at the tail’s base and distributed when a bird preens.
“The key is layers of trapped air contained between overlapping feathers that, when warmed by body heat, act as a cocoon of warmth,” says biologist Gavin Bieber of Wings Birding Tours Worldwide. “Think how a cushy down jacket with an outer waterproofing layer works for us.” As for featherless legs and feet, they’re covered with scales that minimize heat loss.
Behaviors Beat the Cold
When fall food is plentiful, birds gorge to build up insulating fat, which also provides fuel to conserve body heat. Some species switch to higher-fat diets in winter. On sunny days, birds take advantage of solar radiation, turning their backs to the sun to allow their largest surface areas to soak up the rays. Under clouds, they may shiver, which burns calories but increases body temperature.
Roosting is another behavioral adaptation. “Small flocking birds such as bushtits, chickadees, nuthatches and titmice manage cold northern winters by roosting in groups in tight cavities,” Bieber says.
The most extreme survival strategy is torpor: a state of lower metabolism and body temperature that conserves energy. Hummingbirds regularly undergo torpor while swifts, doves and chickadees do so in extreme conditions. The common poorwill can enter a torpor so deep it effectively hibernates—the only bird species known to hibernate through winter. Compared with that, our coats and hats may seem like primitive adaptations indeed.
Help Birds Stay Warm
Even with adaptations to maintain heat, birds can succumb to storms, frigid temperatures and poor food supplies in winter. To help them out:
Provide Quality Food: Select seeds, suet, nuts and other items high in fat and calories to give birds fuel to generate body heat.
Keep Feeders Full: After a cold night, birds need ready access to meals to replenish energy reserves.
Leave flower heads and stalks: Birds feed on seeds and insects that dried flowers and stems provide.
Offer Shelter: Plant evergreen shrubs and trees, build a brush pile or add a roost box to your yard.
Provide Liquid Water: Birds can melt snow to drink, but doing so uses energy needed to maintain body temperature. “Water is as important in the cold months as it is in summer,” says NWF Naturalist David Mizejewski. (Blue jays visit a birdbath in Ontario, Canada, above).
For more wildlife-gardening tips, visit www.nwf.org/nwfgarden.
Melissa Mayntz is a Utah-based writer at birding.about.com
NWF’s Garden for Wildlife™ program provides gardeners with tips about native plants and other elements needed to create nurturing habitats for birds and other wildlife.
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