No endangered species in the Northeast has gone extinct since coming under federal protection, according to a study by an environmental group, and 93 percent have either increased their numbers or become stable.

The report by the Center for Biological Diversity is described as the first long-term study of population trends for endangered species. Researchers looked at 53 species in eight states – Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island and Vermont – that had been listed as federally endangered for at least six years. The success stories included birds such as the Atlantic piping plover and the roseate tern, as well as humpback and blue whales.

The American burying beetle once roamed from Nova Scotia to Florida to South Dakota; now Block Island, R.I., hosts the only native population east of the Mississippi. That population stabilized in the mid-1990s and grew to 577 in 2005. In New Hampshire, the native dwarf cinquefoil, a member of the rose family, landed on the endangered species list in 1980. But scientists rediscovered one small population and planted another, and the flower made it off the list in 2002.

“The data are now in, and it’s clear that the Endangered Species Act is effective,” said the center’s policy director, Kieran Suckling, the author of the report.