December 2, 2013

Winter Chickadees

By Dave Erler

Winter is here; at least that’s what the chickadees are indicating. Even though the first official day of winter isn’t until December 21, the Black-capped Chickadees at the Science Center’s education building know differently. I use birds as my indicator of when the seasons change. Spring arrives for me when I see my first Tree Swallows. Summer is here when I hear the plaintive “peowee” of the Eastern Wood Pewee. Fall is marked by the waves of migrating drab-colored confusing warblers. Chickadees tell me it’s winter by the increase in the amount of black oil sunflower seed I go through in my bird feeders. In early autumn I fill a large tube feeder every other day. Now (the last week of November) the chickadees empty it by the end of the day. Of course other birds are also accepting the handout of sunflower seed, but even with casual observation it’s easy to note the number of pilfering visits the chickadees are making has markedly increased.

It’s fun to see the chickadees come to the feeders. Sometimes I’ll watch as a chickadee very methodically takes just one particular sunflower seed and retreats to a nearby branch. Lacking the strong cone-shaped beak typical of finches the chickadee is incapable of cracking the seed with just its beak. So once perched on the branch it transfers the seed from its beak to its feet. Cradling the seed between the feet it proceeds to chop with its beak to open the seed husk and then quickly consumes the energy-rich kernel. This method works fine but chickadees are better adapted to acrobatically hang upside down to glean insect eggs off the underside of branches than crushing seeds in their beaks.

Flickr/ jon.hayes
More often when I watch chickadees at the feeder I see them grab a seed and fly out of sight. If you are lucky and can follow one, you may be surprise by what you see. Many of these forays result in the sunflower seed being stored in tree bark or wedged into some other small crevice. Research has shown that one individual chickadee will cache hundreds of seeds and be able to recover the seeds over a month later. It isn’t a complete surprise to learn that chickadees not only have more feathers in the winter than summer but that they also have more brain cells in the fall and winter, presumably to help them remember where all those seeds are stored. Having to consume nearly their body weight in food each day during the winter means they are actively refueling their bodies the entire day.

As a bird bander I know from capturing and weighing Black-capped Chickadees in the morning and recapturing the same individuals in late afternoon that it’s not uncommon to find they have gained 1.5 to 2 grams of fat during the day. If you compare an 11-gram Black-capped Chickadee to a 200-pound human that’s equivalent to the human gaining 24 to36 pounds between waking and bedtime!

Besides their ability to eat and store food chickadees exhibit another remarkable adaptation. To survive the long winter night fast they actually lower their body temperature over 20 degrees F. Just like lowering the thermostat in your house saves energy chickadees lower their internal furnace. We do it to save money; chickadees do it to live to see another day.

I know these little black, white, and grey bundles of fluff and energy have been surviving winters for eons of time, but every time I see them on a cold winter morning I am still amazed. They are my symbol of winter and by surviving winter they somehow help me survive winter as well.

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