Here comes the winter solstice -- a time for celebration, because it marks the nadir of the astronomical year and the gradual return to more hours of sunlight.

Here comes the winter solstice -- a time for celebration, because it marks the nadir of the astronomical year and the gradual return to more hours of sunlight.

But first we have to get through what seems an endless parade of drives to and from work in the dark.

No, you are not just imagining that the shortest "day" of the year seems to last an entire month.

Did you know that the earliest sunset this year is at 5:06 p.m., and that it happens every day between Dec. 3 and 13? And that the latest sunrise occurs at 7:55 a.m. -- yes, that's nearly 8 o'clock! -- and that time will hold steady for almost two weeks (Dec. 29 through Jan. 10)?

Until I read a sunset/sunrise chart, I didn't know it either. But it sure explains why darkness is so pervasive from mid-December until mid-January.

It explains why I have trouble squeezing in walks in the parks on work days this time of year. Bring on the sun -- please!

During these long periods, it doesn't seem as if the sun is making any progress at all. No wonder the ancients thought the sun might disappear altogether, then rejoiced when it finally righted itself and the days started to lengthen. Whew!

We may not like these short, dark days, but at least modern man can react quickly to less light and colder temperatures. We merely have to flick a light switch and turn on the heat, and life goes on pretty much as usual.

It's not so easy for plants and wildlife; they have been preparing for months for the winter season.

The lessening sunlight, scientists believe, causes animals to instinctively prepare for winter. How do squirrels know when to gather nuts for winter storage? Why do some animals hibernate and others migrate? Much of their activity can be traced to the sun.

Take the dark-eyed junco, for example. Reacting to waning sunlight three or four months ago, the junco's reproductive organs became inactive and shrunk in size; hormones pushed out new, non-breeding plumage; and the bird started to store fat to prepare for its long migratory flight.

If Mr. Junco had not instinctively started to prepare for winter back in September (when we humans were merrily enjoying our "everlasting" summer), he might be starving to death in northern Canada today instead of visiting bird feeders in Preservation Parks and in my back yard.

Plants, too, set their calendars according to the waxing and waning sunlight -- and the angle of the sun in the sky, for that matter.

The arc of the sun determines how much direct and indirect light hits the earth. Indirect sunlight, which comes from a sun that is low on the horizon, triggers the development of a certain kind of compound in plant cells, while direct light triggers another kind.

The ratio between compounds regulates the hormones that control flowering, leaf drop and bud development -- and even the seeds buried in the ground. The sun-plant relationship is more complex than just photosynthesis; it's amazing, and should remind us that nature is full of mysteries and wonder.

My walks in the park are a little shorter this time of year, but they still fill me with the sights and sounds of nature. I watch a white-tailed deer paw through the woodsy undergrowth on its way to water, food or shelter, and I think about the cycle of the sun and how it has steered the deer's every action this past year.

I ponder on the dormant foliage around me and remember that before long, the sun will lengthen the days and everything will spring back to life.

Mostly, I smile to think that well before the equinox arrives in March, while we humans might be shoveling snow and wearing winter jackets, nature will be heeding the expanding sunlight and preparing for spring.

Sue Hagan is marketing and communications manager for Preservation Parks of Delaware County.