The middle section of the country has just endured three days of what is called the Polar Vortex. For those of us living in the upper Great Lakes region this meant enduring temperatures as low as -34F or more, with deadly windchills reaching into the -50s and 60s. Weather not fit for man nor beast. However, we have the wonderful option of hiding inside our heated homes, while wildlife must find ways to survive these killing temperatures for however long they last.
If you are reading this blog, you are one of the millions of people in this country who care deeply about our songbirds and I’m sure you looked outside and felt deep sympathy for their plight. If you are one of the million who are involved in birdfeeding and not just birdwatching, you can give yourself a pat on the back, because your efforts definitely improved the chances of survival for many birds.
We should understand that the birds that willingly stay north when winter comes have evolved over centuries to survive the extreme cold that occasionally sweeps down from the Arctic. Let’s look at the physical adaptations they
have developed to improve their chances of survival.
Feathers: Anyone who has worn a down jacket or slept under a down comforter knows very well how effective feathers are at providing insulation and warmth. Birds are able to raise or lower their body feathers creating more spaces for air to be trapped and warmed. They also have a preen gland at the base of their tail where they can take oil with their beaks and spread it onto their feathers, adding more insulation and waterproofing. Often when birds are sleeping, they tuck their beaks into their feathers on their shoulder or back to reduce heat loss from their unfeathered beaks. This also allows them to breathe air
that has been warmed and trapped by their feathers
Legs and Feet: Birds are able to control the temperature of their legs and feet by constricting blood flow to their extremities, thereby reducing heat loss.
Torpor: The ability to lower body temperatures, heartbeat and respiration (metabolism) allows bird’s to conserve energy when food is unavailable or during the long, dark nights. Some birds have lowered their body temperatures by as much as 50 degrees, but doing this also means they become less able to respond to threats from predators.
Building up fat supplies: In the autumn all birds, whether they are migrating or not, will build up fat reserves to serve as insulation and extra energy for generating body heat. But severe cold can sap those reserves quickly.
Shivering: Like us, birds shiver to raise their metabolic rate and generate more body heat as a short term solution to extreme cold.
Specific survival behaviors are also very important. For instance, smaller birds like Chickadees and Nuthatches will cluster together in a hole in a tree, an empty nestbox, or even in the branches of a conifer, although an enclosed space is always better. This is known as roosting. We believe the Red-breasted Nuthatches on our property were doing both this and entering torpor because we did not see one of them for the first two days of the extreme temperatures. Birds will wisely choose roost spots that may have residual heat from the day’s sunshine, such as close to the trunk of a tree or near any dark surface.
Solar collection is another technique used to survive the daylight hours. Usually during these severe outbreaks of cold, we are treated to cloudless, sunny skies. In the morning we would look out the window and see a flock of Pine Siskins arrayed on branches of our maple tree soaking up the sunshine. They will often turn their backs to the sun (therefore exposing the largest surface of their bodies to the heat) and raise their feathers slightly. This allows the sun to heat the skin and feathers more efficiently.
You already know what you can do to help the birds. Fill your feeders every morning and again late in the day, so that there will be food available right after dawn. 0ffer the best winter birdfood meaning items high in fat, like Black Oil Sunflower seeds, Suet, and Peanuts. These will provide energy and more body heat. If you can provide a
heated bird bath, you will be helping even more since the birds don’t have to convert bits of snow that they eat into water. We call our birdbath the ‘hot tub” and “spa” as we watch the steam rise and the birds gather around on the rim.
By Kate Crowley