What makes it snow? Where does the snow melt first? Who made those tracks and where did whoever it was go when the tracks end? Wht happens to be the fish when the pond freezes?

Kids have all the questions, and Cris Fleming, a naturalist for the Audubon Naturalist Society, helps them find the answers -- not in boods, but in the field, the thicket, the pond and the big woods of the society's 47-acre estate at Woodend, in Chevy Chase.

Woodend has at least 29 kinds of birds, plus rabbits, raccoons, opossums, squirrels, foxes, shrews, mice, moles, deer and wild turkeys, not to mention all the dogwoods and hemlocks and rosehips and brambles that grow in natural profusion. It also has a variety of programs for kids from four to 18, conducted by naturalists such as Fleming.

"Kids are turned on to nature, anyway. They don't need me," says Fleming, a former kindergarten teacher at the Greenacres School in Rockville. "But they seem to like our programs because we encourage them to handle nature -- there's nothing behind glass. "We want them to take things apart."

This winter, four-and five-year-olds will look for signs of animals in the woods, make bird feeders, and study the wonders of winter. Six-and sever-year-olds will do weather experiments, and play "winter detectives." For eight-, nine- and ten-year-olds there are programs in "skullduggery" -- bones and things -- and orienteeering. Teenagers will stalk owls and birds in a series of field trips.

Nature study, says Fleming, is like detective work: First you look for clues, and then you figure out what they mean. There is ice on the top of the bird bath at Woodend, but a child visitor can see that there is unfrozen water underneath.

"That must mean that the top part gets colder first," says Fleming, explaining that the top is closer to the air and it's the air that does the freezing. And when the top of the pond freezes, the fish just go deeper.

"But how do you feed them if the top is frozen?" worries a child, who is told that there is still food under the water and that fish don't need to eat as much because they don't move around so much in winter.

"Since many of the kids are from the city or from the urban-suburban areas, I like them to spend some of the time just climbing trees or playing in the leaves," says Fleming, leading some visitors under a tunnel of hemlock branches and pointing out a dove that has lighted on a nearby bush. "It's important for kids to feel comfortable in the outdoors... A few kids are scared by nature, and sometimes there's a tendency to step on every insect yoy see. In your house, maybe it's all right to step on insects, I tell them, but this is the insects' house."

In the driveway of the gatehouse, where many of the nature programs start out, there's a small green plant growing and a child wants to know what it is.

"Usually we don't pull up plants," says Fleming, "but since it's in the driveway, pull it up and see if you can tell."

The child examines the roots and finds the seed the plant grew from -- a sunflower seed.

"Those are the seeds we give the birds to eat, but sometimes the birds drop them," Fleming explanins. "And even with all the rocks in this driveway, there's enough soil for the seed to grow in."

When a child finds something long and brown and leathery on the path, Fleming tells her to use her ears.

"Let's listen," says Fleming, shaking the mysterious object. "It sounds like a baby's rattle."

"There are sees inside," deduces the child, who now w ants to know where the pod came from. Fleming tells her to look up, until the child spots some of the same pods high on a honey locust tr ee. That mystery is solved, but there is another waiting just around the bend in the path -- an empty shell of a Chinese chesnut.

"Somebody's been eating something here," concludes a child.

"Somebody?" asks Fleming. "What likes to eat nuts?"

Together, they carefully examine the empty shell and find the clue that will close this case -- the toothmark of a squirrel.