KENNEBUNKPORT – The U.S. Fish and Wildlife Service is investigating last week’s death of a piping plover at Goose Rocks Beach in Kennebunkport.

The piping plover, which nests on sandy beaches from Ogunquit to Georgetown from June through August, is a threatened species protected under the Endangered Species Act.

The dead bird, a fledgling, was found by Maine Audubon biologists.

Only 20 breeding pairs of the shorebird nested in Maine this year, down about two-thirds from the number spotted a few years ago.

“The death of one fledgling doesn’t seem like much until you consider that only 30 chicks in the state have survived to become fledglings so far this season,” said Judy Camuso, a biologist with the state Department of Inland Fisheries and Wildlife, which funds the Piping Plover and Least Tern Recovery Project.

“Since we’re depending on these birds to return to Maine as adults to reproduce, every fledgling, chick and egg is absolutely critical to sustaining the population in future years.

Natural and man-made changes in habitat have limited where the birds can nest, state wildlife officials said, and the chicks are often killed by domestic cats and dogs.

The state wants to step up protection efforts by expanding “essential habitat” zones for the plovers in Old Orchard Beach and Biddeford, a move that would restrict access to nesting areas and give officials some control over nearby activities.

The expansion would add about a mile of beach to the designated essential habitat in each of the two towns.