The lesson of the woods is always new and always the same, but it seems fresher when the reminder is a boy.

For months I had spent much of every weekend hunkered in a blind built over a beaver pond in Southern Maryland in hopes of photographing wood ducks nesting and with their young. Over the winter the landowner and I had put up several sets of nest boxes we hoped would protect the birds from the raccoons, snakes and squirrels that frustrate four out of five nesting attempts in natural tree cavities.

Ducks I had seen aplenty, including woodies, and other splendid creatures from otters to eagles, but there seemed to be no action in the nest boxes.

It was discouraging, and come one rainy Saturday at the end of a hard week I was just too tired to pack up and get going. This was a disappointment to my man Mark, 9, who would pass up candy for a chance to roam the woods and marsh.

"It probably isn't raining there," he said, waving the weather map from the paper.

"Hard to say," I dissembled.

"You could take a nap in the blind."

"I could take a nap here," I grumped.

He kept hanging around, sighing and expatiating on the beauties of the great outdoors. I kept mumbling.

At length he said, "If you really don't want me to talk about it, I won't. But suppose this is when the ducklings come out?"

There was no answer to that one. The one great and simple law of wildlife observation is that skill and knowledge count as nothing compared to time on the ground: If you aren't there, you won't see it.

The rain stopped north of Waldorf, and it was dark but dry when we made camp. Mark put me to bed early, and by dawn I was in the blind, yawning and trying to settle myself into the patient, accepting alertness that is necessary to sustain long empty hours of waiting.

A few minutes after I got the cameras set up, the otters, off for a morning's fishing, zipped past too fast, as always, for me to catch more than blurred pictures of their tails going over the beaver dam.

But the excitement served to get my circulation going, so I was ready when, just as the sun cleared the trees and lighted the brushy margins of the pond, a hen woodie came gliding along with seven week-old ducklings.

She paused and posed like a professional model, turning this way and that and arranging her babies to best advantage. Overeager, I burned up the all the fast film I had loaded in the long-lens camera. Solicitous, she shooed the brood within range of the zoom-lens camera, and when that was empty, closer still for the wide-angle lens. Soon all cameras were empty; she paddled right up to the blind, peering in as though to inquire why the clicking had stopped.

For five long minutes she shepherded the ducklings around and under the blind as I watched through portholes and cracks, afraid to reload the cameras for fear the noise would alarm them. They moved on, working the shallows for bugs and seeds, and melted into the marsh grass.