Wild Birds that do not migrate have interesting strategies for survival in the cold winter, both natural and some that are provided by our caring customers at Wild Birds Unlimited in Grosse Pointe Woods, Michigan. Those customers often ask what they can do to help winter resident birds survive, such as Cardinals, Black-capped Chickadees, and White-breasted Nuthatches that they see in their yards.
Birds survive winter in part by using layers of feathers that they fluff out, trapping air which then insulates them. Fall molt is when birds increase the number of feathers that they have, growing as much as 30% more feathers than in warmer months, adding to their ability to keep out the cold. Smaller birds have more feathers per unit of body weight than larger birds.
The lower legs and feet of birds are tendinous as opposed to having fleshy parts exposed as in mammals. Therefore, there is no heat loss from that area. A birds’ bill is made of horn similar to our fingernails and does not suffer heat loss either.
Birds use their metabolism to produce heat and run a hotter engine in the winter than in the summer months. They produce this additional heat by consuming more food – up to twenty times more on a winter day than during warmer months. Their choice is energy rich foods, which results in a high concentration of glucose in the blood, creating a higher metabolism.
During the cold winter nights, cavity-nesting birds such as chickadees and nuthatches will pile into a tree hollow or a roost box that you provide, sometimes in groups to keep each other warm. In addition, some birds are able to lower their metabolism and body temperature at night, which saves energy. For example, a chickadees’ heart rate slows from 2,000 down to 500 beats per minute and body temperature goes from 108 degrees to twenty degrees lower during the night.
During the daytime, a bird may shiver, with this muscular energy producing heat. Another adaptation to cold is some birds’ ability to store seeds in a crop, an enlargement of the esophagus. This food is used during the night to maintain higher metabolism, especially in finches.
But how does any of this explain the ducks and geese on Michigan’s, Lake St. Clair ice? They have a special adaptation where the arteries and veins in their feet lie next to each other, with the cold returning blood of the veins being warmed by the arterial blood, resulting in no loss of heat.
Mother Nature does a great job of giving birds the tools they can use to survive winter as long as they can find sufficient food. Stock up those bird feeders and utilize your strategy for warmth – a hot drink and a fire!
Enjoy your birds!
Wild Birds Unlimited of Grosse Pointe Woods, MI