Though any bird that survives winter in the North amazes those of us that depend on furnaces and warm blankets, the black-capped chickadee may be the most incredible of all winter survivors.
“Black-capped Chickadees have a wonderful assortment of adaptations for the winter,” said biologist Susan M. Smith, who has studied the black-capped chickadee as long as anyone. “Carefully hidden food items, dense winter coats, specially selected winter roost cavities, and perhaps most remarkable of all, the ability to go into nightly hypothermia, thus conserving large amounts of energy, greatly increases the chances of survival,” she said. The ability to go into regulated hypothermia actually lowers the chickadee’s body temperature in a controlled manner, down to about 12 or 15 degrees (F.) below their normal daytime temperature of 108 degrees (F.). This remarkable adaptation allows the bird to conserve almost 25 percent of its hourly metabolic expenditure when the outside temperature is at freezing. The lower the outside temperature, the more energy conserved, Smith found.
“Chickadees are not the suburban wimps that some people think they are, said wildlife ecologist Margaret Clark Brittingham. For three winters in Wisconsin, she kept track of 576 black-capped chickadees. She found that every winter morning chickadees had to replace the fat they used overnight. As the small birds struggled against starvation and stinging cold, they earned her respect, too. “They are tough survivors that live close to the edge of life,” she observed.
-- George H. Harrison