JUNCOS, JAYS, CARDINALS, nuthataches and other birds of hearty feather that winter in the North are likely to be wondering once again what December is all about. The month began with a series of warm days. Then a stretch of cold snapped in, to be followed by days that were almost balmy. Snow and rain have fallen, fogs have hovered. Skies have been limitless blue and low-hanging gray. The land has been hard and soft. If birds need reasons to migrate South, December has them.

But for all of this formlessness, perhaps what is happening now is little more than winter's annual site of settling in. Nature is moving off into its corner, and the walls on either side tremble slightly with this shifting from summer's activism to winter's passivity. On the land, the final sealing off has yet to occur, even though by calendar time winter begins in a few days. Until the first snow sets the boundary between the seasons, December is less a force than a process. The elements can't be dealt with yet, because uncertainty itself is one of the elements.

Clues may be sought about the severity of the approaching weather, but the "signs" - the amount of berries on pyracantha bushes, the thickness of hair on squirrels' tails - are less than reliable, and probably even teh squirrels bicker about their meaning. What the animals sense, and man should know, is that December is not a month for answers. At best, an observation or two can be made, as when Tu Fu, one of China's greatest poets, wrote in "Travelling Northward":

Screech owls moan in the Yellowing

Mulberry trees. Field mice scurry,

Preparing their holes for winter.

Midnight, we cross an old battlefield.

The Moonlight shines cold on white bones.

The poet reached no conclusions. All he reached was the far side of the battlefield, still uncertain about the coming winter and knowing only that the mice were taking no chances. They were settling in. The waiting was beginning.