I am sure that many of us this winter are thankful to be tucked into our warm, cozy homes during the frigid temperatures and heavy snowfalls. The feeders around the house and are covered with birds and surrounded by squirrels. It is amazing to see the tiny, little American goldfinches, chick-a-dees, and even the Juncos and wonder how they stay warm in such frosty conditions.
Warm-blooded animals like mammals and birds are homeothermic, meaning they control their own body temperature regardless of the temperature of their surroundings. How do mammals and birds do this? Through evolution, adaptations and by the incredible way in which they were made.
We all know that birds have feathers – that is one unique thing that makes them a bird. The main thing that birds have going for them in winter is their down. Down is a specialized feather found underneath all of the other feathers and is soft and fluffy. Many of us have had down coats, vests, and even comforters for the bed or other items. It is because down is so good at trapping warmth. (Down found in coats and vests does not come from songbirds; it comes from chickens, ducks, and geese.) Down is the number one resource that birds have to help stay warm.
Have you ever seen a bird’s foot up close – maybe on a chicken? They are covered with specialized scales that help reduce heat loss. According to about.com, "Birds can also control the temperature of their legs and feet separately from their bodies by constricting blood flow to their extremities, thereby reducing heat loss even further."
Even the smallest bird can get through a freezing winter. Birds build up fat stores in the fall when food supplies are most plentiful. Not only do fat reserves provide insulation and extra energy for generating body heat (according to about.com) fat is then used throughout winter when food is more scarce. Small birds are most vulnerable because it takes more core energy to keep warm; since they have smaller body cores it is more difficult for them to do this efficiently. This is why it’s most important to supply extra seed during the coldest times of the winter. When seed is available, less fat reserve has to be exhausted.
Birds have behavioral adaptations to help them survive winter, too. You may have seen birds all fluffed up on cold winter days as it is snowing and gusting frigid winds. Fluffing feathers in this manner creates air pockets further trapping warm air against their body while their outer feathers are keeping out the cold.
Tucking is another behavioral adaptation. You may have noticed a bird standing on one leg with the other "tucked" up against his body. Another bird may tuck his bill down against his shoulder. Think what you would do if you had only one pocket in your down coat and the temperatures drop. You take turns with your hands in the pocket.
Roosting is a common practice amongst birds trying to stay warm, and if the roosting site is not properly chosen it can be a killer. Bluebirds are especially prone to this one. Many bluebirds fly to southern Missouri and Kansas to escape lower temperatures, and if temperatures drop quickly they roost together. They choose a deep cavity and all pile in. Anywhere from two to 10 birds can be found in one roosting site, dependent on how large the cavity. This can be a bluebird box, for example. If the box is not made of the recommended wood of at least one-inch thickness, the birds will freeze. I witnessed this a few times while I was a nature center manager.
During this last storm, I hope you were able to spread some birdseed, get a mug of hot chocolate and watch the birds. Tallyho!
Reach Lynn Youngblood at TheGreenSpace@sbcglobal.net.