Winter presents several challenges for our birds, especially when temperatures drop below freezing. We often don’t think or wonder how our birds survive cold nights, we just know that they do or at least hope they do. Even those times in the Deep South, desert regions, or the Pacific coast where a cold snap or several inches or feet of snow fall can affect a bird population. Winter brings extremely cold temperatures, strong winds, snow, and rain.
The nights seem to last forever. 16 hours of darkness and in some places more. That doesn’t leave a lot of time to drill and feed. However, many birds must at least triple their normal intake to survive and do so in half the time. Every winter we lose many of our feathered friends to the rigors of winter. This is how “nature” works. Survival of the fittest, Passing on the strongest genes.
Birds have many adaptations to survive the extremes of winter. Some birds migrate, others adjust their eating habits. Birds like chickadees and goldfinches add feathers in preparation for winter. The typical chickadee or goldfinch is covered with about 1,000 feathers during the summer. By winter, they have doubled that number to more than 2,000 feathers. For a small bird, that can mean a lot of extra bulk and weight.
During a cold, windy, or just plain unpleasant day, the birds will fluff their feathers. By doing this, they create pockets of dead air, much like insulation or a double pain window. This reduces heat loss by up to 30%. Extra feathers and fluff are not enough to get you through a cold winter day, but only cold, long, dark nights.
Birds also have a unique circulatory system in their legs to help them cope with cold temperatures.
Pay attention now.
The warm arterial blood from the interior of the birds, which is directed to the legs and feet of the birds, passes through a network of small passages that runs along the veins of cold blood that return from the legs. The network of vessels acts as a radiator and exchanges the heat from the warm arterial blood that exits to the cold venous blood. By heating old blood, no heat is lost and the feet receive a constant supply of life-sustaining blood. This is also the reason why waterfowl can swim in almost icy waters and not get cold.
Fat is another important adaptation for winter weather survival. Fat acts as an insulator as well as an energy reserve. During the day, the birds eat to build fat stores. On average, a bird can accumulate up to 15% to 20% of its body weight in fat before it is too heavy to fly.
Now remember, the days are shorter and colder. Birds have to eat enough to survive the day and replenish fat stores. The smaller the bird, the higher the metabolism (more energy burned). Birds do not have brown fat, like we do, but have white fat. White fat is a high-energy fuel used to power the heating process in birds.
Shaking
Thermogenesis is a fancy name for chills. You can’t really see it, but all the birds tremble in the cold of winter. From the largest birds like eagles and waterfowl to the smallest birds like hummingbirds. They all shiver to keep their core body temperature between 106 and 109 degrees, depending on the species.
Chills produce heat five times more than normal basel speed and can maintain a normal body temperature for six to eight hours at temperatures that drop to minus 70 degrees Fahrenheit. Without shivering, the bird’s body temperature would drop rapidly and the bird would become hypothermic.
At night, birds like the chickadee have chills, or lack of one more step. To conserve heat and energy, chickadees can lower their body temperature by interrupting their tremors. These periods of inactivity allow the bird’s body temperature to cool slowly, until it drops about 10 to 12 degrees. At this point, the bird enters a state of unconsciousness called lethargy. Your breathing and heart rate will also decrease during this period.
Energizing
As morning approaches, the periods of inactivity decrease until the bird is constantly shivering again. The body temperature returns to the normal range and the bird regains consciousness. The result of this torpid state is energy savings of up to 20% during a typical winter night.
Conserving energy is very important considering how little fat a bird can store. Based on a 15% daily increase in body fat, a typical chickadee has around 16-24 hours of fat or energy stores to support a winter night. That is why, my friend, it is imperative that a bird leaves early in the morning and stays up late to forage for food regardless of the weather.
If you do not replenish its fat stores every day, the bird will not have enough energy to get through the next night and will die. There was a time when the natural world provided food for most wild animals. With the constant reduction of habitat, winter protection and food supplies continue to shrink.
You can increase the odds for birds and some mammals simply by filling their feeders with their favorite food and offering tallow. Fresh water is also important. When birds are required to eat frozen snow, it takes valuable energy to heat that snow as it travels through it.
Next time you’re out in the cold or even hot to fill your feeders, think about this: “Nature” has provided birds with some wonderful tools to survive, whether it’s migration, blood circulation, diet change, extra feathers, or shivering. .
Birds are truly wonderful for us to enjoy. In some ways, it is unfortunate that many birds now need our help to survive. However, look at the education and joy we get from caring for and feeding our birds.
