THE DEEP FREEZE is on, but few examples of its effect were as startling as one we witnessed the other morning. A female cardinal, feathers ruffly as it left the branch of a birch, came in for a landing. Its wings opened about a foot above the ground and its beak was slanted low to cut into the wind. But on touching down, the bird must have felt a sensation new to its experience and genes: it slid and fell. The snow, coated with ice, was a sheet of ungrippable whiteness. For the cardinal, its claws meant nothing, neither to break the slide nor to help the unbalanced birt to get airborne again. The creature had lost hold, a sudden breaking of ties to a habit formed by all the effortlessly sure landings the earth had provided before. The slippery ways of reality were now a factor, and the cardinal perceived that this was a different winter.

For the bird, and for all others now looking upon the unfamiliar face of chilling Janus, the difference is the ice. Human beings, like birds, like traction. The head is meant to deal with the uncertainies of life, the feet are not. If we must choose our fates, we put ice second, as did Robert Frost in his wry poem, "Fire and Ice":

Some say the world will end in fire,

Some say in ice.

From what I've tasted of desire

I hold with those who favor fire.

But if it had to perish twice,

I think I know enough of hate

To say that for destruction ice

Is also great

And would suffice.

Poems are cold comfort to the animals and birds whose bodies are under attack by the merciless winter. Many creatures that have survived other Januaries will not make it through this one. But for all of the death and agony, nature is no less a sure guardian. Now dying off are the weaker of the species; the creatures that survive are the stronger ones, meaning that a heartier breed is evolving. Where it is leading, we don't know, except that eons from now, if the cold grows colder, the cardinal may light upon the ice of January and not fall when it slides. If the earth is tens of millions of years old, such a new skill learned in only a few hundred thousand years will be speedy progress.