In the warmth of Riverbend Nature Center, youngsters kneel, sit or stand in front of a picture window and watch birds light on the feeders outside. A tufted titmouse cracks a seed with its beak. A little Carolina chickadee flicks in for food, then quickly away again. A cardinal perches on a pine. A red-bellied woodpecker, in search of a lingering insect, hits up the bark of a nearby tree, and after a few futile tries flies to the suet feeder.

You can't always make it to the woods or the nature center, but you can bring the birds to you. You can watch them on your own home-made feeder. It's like having a pet you don't have to clean up after.

Of course, watching them is only the bonus. You feed them to help them survive the winter when their natural food supply is locked up by the cold. And once you start feeding them, you'll find they quickly come to rely on your food supply.

One of the simplest birdfeeders is made from a plastic gallon milk jug. With a knife, carve out of a five-inch square close to the base. That's where you'll put food. To make a perch, poke two holes across from each other in two uncut sides of the jug. Push a long twig through both holes. (Birds sincerely love anything natural, like branches.) With an ice pick, make a hole in the metal cap. Through the hole from the inside, pull a strong piece of wire with a stick tied on the end. Insulated electrical cord does nicely. The stick on the end catches below the cap to keep the wire from slipping out the hole. Tie the wire to a tree limb - a limb just large enough to support feeder and bird discourages squirrels from raiding your feed supply.

Another easy-to-make birdfeeder is a half coconut shell. Drill three or four holes in the edge and suspend it with strong string or wire. The other half can be used as a rood.

Best of all is make-shift shelf on a sunny window sill. You can tack down a cookie sheet with 1 1/2-inch raised sides that prevent seeds from blowing off in the wind. A wooden shelf with small branches nailed around the edge for seed containment looks like home to birds. There you can put seeds and grapefruit shells full of dried fruit or hardened melted suet. To keep off the snow, put a roof on your feeding station. Nail two sideboards perpendicular to the self to prop up a plywood roof of equal size. Put dabs of peanut butter on the underside of the roofs; wrens love to hop up for beakfuls.

Be sure you put out a dish of water. Birds especially need it now, and will even bathe in it in freezing temperatures. On your windowsill, the water will be slower to freeze.

Now, to bring on the birds, let them know you're there by scattering bread and seeds on your lawn. The birds should get braver and find their way to the feeder. Peanut butter in your feeder will entice the little beasties with its strong smell. It's a good idea to continue to scatter seeds on the ground, because some species, like cardinals and sparrows, prefer feeding there.

Cereal grains, such as corn, wheat, oats and millet are basics for all species. Scatter corn away from the house to keep pigeons, crows and starlings from your feeders. The more attractive birds love the more expensive sunflower seeds. When you buy them, or mixed wildbird seed, see that you are getting seeds, not a high percentage of filler. Start off with a small bag, maybe three pounds. If that's used up in a week, graduate to the 25-pound economy size, because you'll be feeding birds till leaves come out on the trees.

No bird-feeding station is complete without suet, enjoyed by insect-eaters like woodpeckers, chickadees and titmice. You can get beef suet from your grocery store's butcher, sometimes for no charge. Or use hardened bacon fat, not too salty. Stretch it by adding cornmeal or even stale doughnut pieces.

To make a suet-holder, take a net onion bag and cut off a large enough part to wrap a three-inch piece of suet. Hang it from a tree limb. Compulsively neat people may want to knit or crochet suet bags. Or you can tie suet directly to a branch by wrapping a piece of soft twine around and around it.

Suet packed into a hanging pine cone, or even rubbed onto the bark of trees, provides fat that helps birds maintain their high body temperature. If you do rub suet or peanut butter onto tree bark, don't do it on the south side of the tree. The stuff will probably melt in stronger sunlight and run onto the ground.

Another simple and attractive suet feeder can be fashioned from a short log. Drill holes, an inch in diameter, every few inches in a foot-long log about six inches around. Screw a metal eye - bought at a hardware store - into the top of the log so you can hang it by twine to a tree limb. Pack suet into the holes. If you want to keep off less desirable birds such as English sparrows and starlings, remove the bark from the log, and they won't be able to get a foothold. Try not to feel guilty about that.

Many birders recommend mixing a little sand with birds' food. Birds eating from feeders don't get the grit they're used to picking up when feeding in the wild. Sand is needed to aid in digestion. Without grit, birds with plenty of available food can starve. Youcan buy pulverized shells at pet shops to use as grit. If you use beach sand, wash and dry it first.

It's helpful, too, in snowy weather, to uncover a patch of ground where birds can scratch away.

Kids can make this snack for the birds: BIRD BROWNIES 1 1/2 cups of suet 1 cup of granola or grapenuts 1/2 cup of crushed peanuts 1/2 cup of raisins two pinches of sand

In a cakepan, melt suet very slowly so it doesn't burn. Stir in dry ingredients. Put mixture in freezer. When frozen, cut into brownies. Wrap brownies in suet bag and hang it from a branch.