SOUTH KINGSTOWN, R.I. -- The piping plover is a small whistling sea bird with spindly legs. Four plovers migrate each summer to Moonstone Beach, a wildlife refuge here where the endangered species is afforded federal protection.

Well-oiled nudists also migrate here by the thousands on hot summer weekends because this is one of the last beaches in New England where people may doff their clothes without fear of arrest.

The federal government has proposed that the plover have exclusive summer rights to the 1 1/2-mile barrier beach. The nudists, who also feel endangered, say there's room to share.

Both sides are scheduled to square off at a public hearing tonight -- the birds represented by members of the U.S. Fish and Wildlife Service. It promises to be, one nudist quipped at the beach the other day, "the ultimate confrontation between the piping plover and the jaybird."

Moonstone Beach is part of the Trustom Pond National Wildlife Refuge, 1,000 acres of woodlands, meadows and beach that overlook Block Island Sound.

The Fish and Wildlife Service owns and manages the property and considers of utmost concern its responsibility to protect two pairs of plovers and 12 pairs of least tern, a sea bird proposed for protection under the 1986 federal Endangered Species Act.

"We are not an appendage of the National Park Service," said Charles W. Blair, the refuge manager. "By congressional mandate, wildlife comes first here. People are invited to share the beauty -- but only if their uses are compatible with the life we're charged with protecting."

But Joseph Di Pippo, founder of the New England Naturist Association and for almost 20 years an enthusiast of sunbathing in the buff at Moonstone, believes nudists, who are now confined to 700 feet of the beach, can live harmoniously with the plover.

"The bird shouldn't have it all, nor should we. There's got to be some space for compromise here," Di Pippo explained from behind a pair of sunglasses this week, noting that he and many other nudists planned on making the point at tonight's hearing.

The plover migrates from the Gulf states to the coastal New England area each summer to hatch and raise its young. The eggs look very similar to beach stones -- which people step on and animals eat.

Two years ago the Fish and Wildlife Service fenced off all but about 2,000 feet of Moonstone for the plover and now proposes closing the remainder of the beach during the summer nesting season.

Blair predicts the action will allow plovers to increase to seven nesting pairs in the next decade; naturists predict it will all but quash their fledgling nudist movement.

Naturists are nudists who define themselves as "clothing-optional" enthusiasts who find freedom relating to their naked beginnings but don't confine themselves to "nudist ghettos."

Paid membership in the four-year-old New England Naturist Association is now 1,400, according to Di Pippo, with about 10,000 members in the National Naturists Society.

The road to the beach has hardly been smooth for nudists in New England. They lost access to the Cape Cod National Seashore in 1975 when a federal appeals court upheld a National Parks Service regulation against nudity on the Cape.

Last summer, the piping plover and a Newbury bylaw against nudism eliminated Plum Island in the Parker River Wildlife Refuge as a clothing-optional hide-out. And the six-ounce plover is the odds-on favorite to win the battle of Moonstone this summer.

"What's the big American hang-up with our kind of body acceptance?" asked Melinda Herbert, a resident of Katonah, N.Y., who said she has been coming to Moonstone with her husband James for the first week in June for the past four years.

She and about 200 other sunbathers basked in Monday's warmth in the unfenced section of Moonstone abutting 800 feet of beach used by the town of South Kingstown by special permit from the Wildlife Service.

The town has purchased another beach that will give residents water access regardless of what happens at Moonstone, but there would be no provision for nudists.

Police Chief Vincent Vespia Jr. said the nudists are "not a law enforcement problem because they do a very good job policing themselves." He noted there were occasional exceptions -- Alma Hanson, for instance, recalled several.

"I stopped going to Moonstone because there always seemed to be two or three men who strolled beyond the borders just to try to impress us," the Kingston resident said.

No signs or markers post the nudist area except a log of driftwood on one side and a wildlife sign on the other. Last Sunday's heat brought about 2,500 to the pocket of beach. A very busy day permits each of perhaps 4,500 sunbathers about a 6-by-6-foot square of sand at high tide.

Nelson Holmes of Bradford, R.I., protected by sunglasses and a visor inscribed with the word "Freedom," explained that he frequently brings his grandchildren here.

"I think the truth is that some people think we're perverts," Holmes said.

A Piper airplane buzzed the beach about 50 feet overhead, its gawking pilot clearly visible in the window. This, someone else commented, was about the only kind of bird they ever see on this patch of Moonstone.