How Birds Stay Warm Through a Copper Country Winter

Winter birding in the Copper Country is a special thing. With snow on the ground and temperatures dropping well below freezing, the birds we see are doing something remarkable: they are surviving long, cold months that would quickly overwhelm an unprepared body.

Survival through winter isn’t magic. It’s the result of a suite of physical adaptations, behavioral strategies, and energetic decisions that allow birds to maintain body heat, find enough fuel, and endure conditions that would challenge most mammals.

Heat Retention: Feathers and Insulation

The first line of defense against winter’s bite is feathers. Birds have feathers that act very much like a down-filled winter coat – trapping warm air close to the body and keeping the cold out. Many northern species grow extra feathers and down in fall, and birds often fluff their feathers when temperatures drop to create more insulating air pockets around their bodies.

By fluffing their feathers, small birds trap insulating air close to their bodies, helping them conserve heat during cold winter days.

Waterproofing matters too. Birds preen oils secreted from their uropygeal gland (located dorsally at the base of the tail) onto their feathers. This helps keep their feathers cleans and repels moisture. Dry clean feathers insulate far better than a dirty wet ones, so keeping plumage clean in snowy conditions is itself a survival strategy.

Keeping the Core Hot, Letting Extremities Cool

Most birds maintain a very high core body temperature – 102°F to 109°F (39°C to 43°C) – even in frigid weather. However, heat loss through bare parts like legs and bills can be a major issue.

To solve this, many birds employ a counter-current heat exchange system in their legs and feet: warm arterial blood moving out to the extremities warms the colder venous blood returning to the body, minimizing overall heat loss. Some species also tuck one leg into their feathers or alternate legs to balance warmth and blood flow.

Countercurrent heat exchange: Blood vessel networks warm blood as it moves from the foot back to the body. This temperature difference (yellow arrows) limits heat loss and saves energy. Graphics by Cornell Lab of Ornithology (https://www.allaboutbirds.org/news/how-do-gulls-deal-with-cold-feet/).

Smaller birds like chickadees may let their feet get very cold (near freezing), because keeping them at core temperature would cost too much energy. Their bodies are built to tolerate cooler extremities without damage.

Fuel for Heat: Eating and Fat Reserves

Staying warm is just as much about energy intake as it is about insulation. Birds burn calories to generate internal heat, and winter drastically reduces the daytime hours available for foraging. Bird metabolism increases dramatically in cold conditions, and many species must eat almost continuously during daylight to build fat reserves that fuel shivering and heat production overnight.

High-energy foods are critical in winter. Birds must eat frequently during daylight hours to build fat reserves that fuel heat production overnight.

That’s why winter bird feeding stations often see birds like chickadees, nuthatches, and woodpeckers returning again and again to high-fat foods like suet and sunflower seeds: these calorie-dense fuels are effective at fueling heat production.

Behavioral Strategies: Shelter, Huddling, and Roosting

Surviving night and wind requires more than body heat and calories:

Finding Shelter

Dense evergreen foliage, tree cavities, and even manmade structures provide critical wind protection and warmer microclimates at night and during storms. Birds instinctively seek these sheltered spots when temperatures drop.

With a large body size and a lower surface-to-volume ratio, Great Horned Owls lose heat more slowly than smaller birds. An open-faced nest box still offers important protection from wind and snow, reducing heat loss during winter. (Screen capture from the Copper Country Bird Club's Great-horned Owl Nestbox cam at Skyline Center, Hancock, MI.)

Group Warmth

Some small species huddle together at night or during storms. By clustering tightly in sheltered spots, birds can share body warmth and reduce individual energy expenditure.

Reducing Heat Loss Overnight

Certain small birds may allow their body temperature to drop slightly at night – a controlled physiological strategy called torpor – to reduce the gradient between body and air temperature, thereby saving precious energy.

Species-Specific Survival Tactics

Different bird species rely on different combinations of physiology and behavior to survive winter conditions in the Copper Country.

• Chickadees and Nuthatches Small body size means rapid heat loss, so these birds forage almost continuously during daylight hours to build fat reserves. They commonly use tree cavities or dense vegetation for nighttime shelter. Chickadees may roost alone or in small groups depending on conditions, balancing warmth, space, and safety.

• Kinglets Among the smallest winter birds in the region, kinglets depend heavily on dense conifer cover that blocks wind and creates slightly warmer microclimates. They often roost communally in sheltered locations, a behavior that can significantly reduce overnight heat loss.

• Woodpeckers Woodpeckers benefit from insulated tree cavities that protect them from wind and cold. Many species excavate multiple roost holes and select the most sheltered option during severe weather, while continuing to access insects hidden beneath bark and within wood.

• Crows and Ravens Their larger body size slows heat loss, and both species often form large communal winter roosts. These roosts are thought to reduce predation risk and take advantage of favorable microclimates. Any shared warmth from nearby birds is likely a secondary benefit rather than the primary reason for roosting together.

  
  

What This Means for Birders in the Copper Country

The next time you see a black-capped chickadee fluffed out against the cold or a woodpecker tapping through snow-covered bark, remember: their winter survival is the result of adaptations honed by generations existing in northern climates.

Whether you're watching birds from your windows on a sub-zero Fahrenheit day or hiking into the snow to see them, understanding that these birds are constantly balancing heat generation, energy use, and risk helps us appreciate not just where birds are in winter – but how they’re thriving amid conditions that would overwhelm so many other creatures.

How You Can Help Winter Birds

• Keep feeders stocked with high-fat, high-energy foods

• Provide reliable water sources (heated if possible)

• Preserve natural shelters like dead trees and dense evergreens

• Place feeders near cover so birds can retreat quickly from wind and predators