The belief that Hawaii was an unspoiled paradise before the Europeans colonized and despoiled it has been proven wrong, according to a new study by two Smithsonian scientists.

The Polynesians, the study says, had already destroyed much land and had burned or hunted into extinction 39 species of birds -- apparently half of all the varieties on the islands -- before the arrival of Capt. James Cook in 1778.

In the Aug. 13 issue of the journal Science, Storrs L. Olson and Helen F. James write that in a 10-year survey of fossils on the Hawaiian Islands they found 74 different kinds of fossil birds.

But today, less than 20 of the species can be seen in the islands. By using carbon dating and other archeological techniques, the two researchers found that 39 of the missing species probably became extinct after 400 to 600 A.D., the time when the Polynesian natives colonized the island.

Ancient hearths have yielded the charred bones of some of the extinct birds -- they were apparently hunted and eaten by the early Polynesians. A number of the extinct birds were flightless geese and ibises, which would have been easy prey for the islanders.

But the massive disappearance of birds cannot be accounted for by hunting alone, the researchers wrote. A more plausible explanation for the disappearance is the burning off of whole lowland forests by the islanders to set up farms.

"Journals of early western voyagers to the islands, including those of James Cook, James King and George Vancouver, record extensive deforestation and heavy cultivation . . . as well as the use of fire in clearing," the researchers report.

In the 200 years of European colonization, about a dozen more species native to the islands, or one-third of those still left, were extinguished.

One of the chief clues that the 39 extinct species existed when the Polynesians arrived, apart from individual findings at hearth sites, is the presence of a rat in the layers of fossil rock. It is known that the rat was brought to the islands by the Polynesians accidentally when the islands were colonized. The extinct bird species have been found alongside fossils of the rats, showing they existed side-by-side.

But by the time Cook arrived and records began to be kept, the species were gone.