Full Moon Phenology: December

For those who awoke early on December 10, the coldest morning of the year so far, a rare celestial event accompanied the setting of the 
full moon. A lunar eclipse began to darken the moon as it approached the western horizon while simultaneously entering the earth's shadow. The eclipse itself wasn't the rarity (nor that the sky was crystal clear for such an event), but rather the fact that at our longitude we could see the risingsun and an eclipsed moon at the same time, a phenomenon known as selenelion.

If you think about it, this doesn't seem possible: the whole point of a lunar eclipse is that the earth sits directly on a line between the sun and the moon. If you can see both in their entirety, how can our planet be shadowing one from the other? The biggest part of the answer: refraction of light by the earth's atmosphere makes celestial bodies appear higher above the horizon than they actually are.

I was up before sunrise to start a fire and aware of the eclipse, but our western horizon is obstructed by megatons of limestone, dirt, maple, and oak. As we were down to our last positive degree of Fahrenheit outside, I opted against a hike to the ridge, went back to a warm bed and listened to the stove begin to pop and roar downstairs.

The ground finally froze solid in early December, and now it's ready for a deep insulating blanket of shimmering white. The last of the migratory birds have fled for destinations tropical, or at least more temperate. One puzzle for me was the regular flocks of large birds of peculiar voice that I had seen heading not south but decidedly east over our hollow during the last moon.

Canada geese seem to fly every which way in the off season, but these flocks did not honk and all flew on the same trajectory, suggesting O'Hare and Midway more than the Delta or the Yucatan. They were Tundra Swans (Cygnus columbianus), headed from their breeding grounds in the treeless north of the Yukon, the Mackenzie, and Hudson Bay to their winter grounds on the Chesapeake and the Outer Banks after a length pit stop at pool 8 on the Mississippi.

I haven't seen swans this month, but while I was writing this moon's installment, I heard Cabin Dave on WDRT's "The Sweet Sunny North"
telling of his recent sighting of Tundra Swans on Lake Kegonsa in Stoughton. He also reported that lake ice was finally forming, further encouragement for the birds to move along.

What's left after this mass evacuation of bird talent? Our feeder groupies: the chickadees, nuthatches, cardinals, titmouses, siskins and finches. We hung the remains of a recently skinned raccoon in the center of a lilac bush, and the woodpeckers have already made it a neighborhood hangout.

Higher up the food chain, I am often hearing Eastern Screech Owls (Otus asio) in the early dark, peeping and mewing from the dense cedars. In the spring, those notes can invite mobbing behavior from nesting songbirds, but all young are now fledged and gone south, or fully capable of dashing to the safety of feeders.

Look for Snowy Owls in the Driftless this winter. A notable irruption of Nyctea scandiaca has been documented already throughout Wisconsin and across the northern tier of states due to lemming failure in the north. (Don’t believe reports that this has anything to do with the Canadian exchange rate.) I was already once fooled by the winter plumage of a Red-tailed Hawk, which had shouldered up on a treetop and looked surprisingly owlish from a distance.

All who pine for more light in their lives can rejoice that the earliest sunset of the year--which actually comes before the winter solstice--arrived at the same time as the December full moon. We have already gained a couple of minutes of late afternoon light. But even when the days begin to grow longer, the sunrise will keep getting later into early January. The elongated and unbalanced figure 8 often printed on a globe is a graphic representation of this phenomenon. This curve is called an analemma, and despite what I believed in third grade, it is not a giant floating Hot Wheels track in the Pacific Ocean.


Michael Nordskog