Winter Solstice

Winter solstice is two days away, on Friday, the 21^st, at 4:12 a.m. Where I live the day will be 9 hours, 16 minutes, and 3 seconds long. The sun will be “standing still.” (The origin of the word solstice comes from the Latin solstitium, from sol sun + -stit-, -stes standing). Even though we celebrate solstice because it signals longer days, it’s just the beginning of winter. The weather gets colder, because the earth’s temperature will continue to drop as it gives up retained heat from summer and spring. Sunrises won’t be earlier until January, because it is later sunsets rather than sunrises that increase the length of daylight  (http://www.timeanddate.com/worldclock/astronomy.html?n=1947).

Winter has already begun here. Today is 22 degrees, but with the wind it feels like 10, and the sky is overcast. Birds and squirrels have disappeared from my yard and are in a state of torpor that they will arise from as the sun appears and temperatures increase. In this state of temporary sleep, metabolism slows, along with heart rate, respiration, and body temperature.

Birds are much better equipped to survive cold than heat (see the lecture about metabolism on the terrific site http://ornithology.com/ ). Feathers are incredible insulators and are a bird’s first defense against frigid weather. Other mechanisms or adaptations that allow birds to survive low temperatures include roosting in flocks, tucking their heads into their bodies so that a smaller area of mass is exposed to the cold, and fluffing their feathers.

Perhaps the most relevant question for the pedestrian naturalist is, how can we help the birds as they emerge from their sleep? Birds raise their metabolism by sunning themselves and by shivering. Shivering consumes a great deal of energy, which means birds need ready access to quality food. They also need access to water. Even though they can eat snow, doing so cools their systems, and so it’s far better for them to drink water that we can provide. Winter technically arrives with solstice, but for birds and mammals, winter arrives when it arrives.