PIRU, Calif. (AP) _ More oil leaked from an earthquake-ruptured pipeline than was previously thought, and the spill's final environmental impact may never be known, officials said.

A 12-mile stretch of the Santa Clara River was contaminated by oil that leaked from an Atlantic Richfield Co. pipeline in Valencia that ruptured in the 6.6-magnitude earthquake on Jan. 17.

So far, the carcasses of 65 oiled birds, reptiles and mammals have been found. The spill also killed more than 600 fish, including several unarmored three-spine stickleback, an endangered species.

Now biologists are saying many small birds such as finches, gnatcatchers, vireos and orioles will fly away before they are killed by the oil. Larger birds of prey that feed on oily fish or rodents also can fly far away before dying, and turtles, toads and lizards crawl under rocks to die.

''This spill is having a greater effect on wildlife than the numbers of dead animals indicate,'' said Bob Schlichting, a spokesman for the Department of Fish and Game. ''We may never get the numbers of all the affected birds.''

''And even if they don't die outright, their reproduction may be affected when breeding season begins in February,'' Schlichting said Friday.

Arco officials first estimated that 147,000 gallons spilled, then revised that figure to 172,000 gallons. New figures from the state Department of Fish and Game show 214,000 gallons escaped.

Arco spokesman Albert Greenstein said about 64,000 gallons of oil has been retrieved, and much of the remainder has evaporated or been absorbed into the soil.