Eleven wilderness islands in the Potomac River upstream from Washington were given to the state of Maryland today by a national conservation group that said the richly forested preserves are home to giant, red crested woodpeckers and possibly even a bobcat.

The islands, once owned by Christian Heurich Jr., the late Washington brewer and real estate magnate, are 22 miles northwest of Washington near Seneca, Md.

With their treasures of century-old chestnut oaks and ancient Indian ruins, the islands, said Nature Conservancy President Patrick Noonan, remain today "the way Maryland was when the Ark and the Dove came up the St. Mary's River" with the state's first settlers in 1634.

The islands will remain open to the public, but under terms of the private, nonprofit conservancy's gift, hunting and trapping will be prohibited.

"We're at a time in history when either those islands are brought to public ownership or . . . become rows of cottages up and down like the Chesapeake Bay," said James B. Coulter, Maryland's secretary of natural resources.

Coulter and Gov. Harry Hughes accepted the deed to the islands from the Nature Conservancy in a ceremony at the State House.

Heurich bought the islands and a 22-acre parcel on the nearby Maryland shore for about $110,000 and later gave them to the conservancy with the understanding that they ultimately would be turned over to the public.

The donation includes Norbell, Submarine, Grapevine and Poteau islands, part of Watkins Island and six unnamed islands.

They will be prime areas for study as the state begins the Maryland Natural Heritage Program to identify the plants, wildlife and natural wonders typical of Maryland and plot plans to preserve the rare and endangered among them. The $450,000 program, funded by the state and federal governments and the Nature Conservancy, was announced as the state accepted the deed to the islands.

Within a month, scientists will begin combining library and museum records and interviewing local ecologists to learn about the environment from the salt marshes on the Chesapeake Bay to the mountain forests of Western Maryland, according to John Nutter of the conservancy, who directs the heritage programs in 22 other states.

Scientists already know from previous observation of the newly acquired islands that they will find deer, snapping turtles, blue herons, songbirds and the pileated woodpecker, a giant species of woodpecker with a red crest, a black-and-white neck and a loud call. There is also evidence on Watkins Island of bobcats, which would be unusual because these predatory animals are often the first to disappear in a changing environment, according to conservacny spokesman Jack Lynn.

The islands, so lush will vegetation that the trails are overgrown, are forested with sycamore, walnut, poplar, oak and black locust trees. Previous archeological excavations indicate that Indians inhabited the islands even before 500 B.C., the conservancy officials said.

Not far from the islands, man already is making his mark on some privately owned isles by setting up hunting camps according to the conservancy's Noonan. o

But Secretary Coulter said he hopes that today's island gift will be the beginning of state acquisition programs to preserve more of the scores of islands that dot the Potomac.

Nearly half of Watkins Island still is owned by two individuals, but Noonan indicated the Conservancy is hoping they won't keep or develop it.

"We're trying to educate them as to the beauty of gifts of land," he said.