They are small shy creatures that only come out at night, gliding through the air from tree to tree in search of food. But far from being rare, naturalists say, flying squirrels are at least as numerous as their daylight cousins, gray squirrels. And the next couple of weeks may be the last good chance to see them for months.

"They are so very, very common, but nobody knows about them," said David Farner, senior naturalist at the Audubon Naturalist Society. "They seem like an exotic creature, but they are in most people's back yards-but they don't know."

These hidden-in-plain-view animals are seldom seen because most people do not make a habit of standing under tall hardwood trees a half-hour after sunset or before sunrise, the best times to see them. The squirrels also will come to bird feeders or tree trunks baited with treats.

They are about half the size o gray squirrels, with gray-brown fur and a distinctive white belly that stands out in the dark. They do not fly so much as glide, stretching their paws to make a wing out of a fold of skin that extends from the wrist of each front leg to the ankle of each rear leg. (It is a membrane, called a patagium) They use their tails as rudders.

Flying squirrels made the news in January, when scientists in China announced that they had found the fossilized remains of a dinosaur that was the ancestor of birds. It glided, lived strictly in trees, and its appearance was compared with the flying squirrel.

The species in this area are Southern flying squirrels, which despite their name can be found from Canada to Mexico. They nest in tree holes, preferably hickories but also beech and oak.

They were out in force the other night, chirping quietly, at the Long Branch Nature Center in Arlington, which puts nuts, birdseed and peanut butter on a platform attached to a tree a few feet away from an outdoor deck. Half a dozen waited nervously on the tree trunk as another quickly grabbed a peanut and fled. They did not seem to mind glashilihgts, a video camara and chatter from a small group of people.

Most glided in from a few feet away. Occasionally, though, a small form launched itself 20 feet or more to a smooth landing. Glides up to 240 feet have been recorded, according to the Marlyand Department of Natural Resources.

"They are not shy of people; they are jus shy of other animals," said alonso Abugattas, a Long Branch naturalist. Owls love to eat them, as do roaming house cats.

The nature center is closed after dark but offers several flying squirrel observation seesions a year. The next on is March 8; reservations are required, and the nature center may add a session if that one fills up.

"We have 25 people at a time sitting there with their flashes going," Abugattas said, "and they are a little nervous, but they keep eating."

The cold months are a the best time to see them. They live in social groups, eat mainly seeds and nuts and concentrate their foraging at dusk and dawn. In spring, males become more territotiral and pregnant females hide. They switch to a insect diest in summer, and fee all through the night. They also are known to eat bird eggs and nestlings if they can get them.

Farner offers this advice to attract flying squirrels: Smear some peanut butter on a tall tree shortly after sunset, agter birds and gray squirrels are no longer active. Before they get up in the morning, check whther the snack has disappeared or has teeth marks. Put food out each night to get the flying squirrels accustomed to it, and then stay around to see them show up to feast.

Of course, it might be raccoons taking your peanut butter, but try to be optimistic.