PORTLAND – Biologists are hoping to lure rare terns to a Casco Bay island for the first time since 1914.

National Audubon Society staff began unloading equipment last week on Outer Green Island. A team of students will use decoys and recordings of courtship sounds to attract common terns, endangered roseate terns and perhaps even some arctic terns looking for a place to nest and raise their young.

If the project is successful, Outer Green would be the only island in the bay with nesting terns.

The Gulf of Maine Seabird Working Group, a coalition of biologists from state agencies and nonprofit groups in New England and Canada, approved the project in August. It’s part of a larger effort to protect seabirds and restore their historic nesting areas along the Maine coast.

A project on Jenny Island in the eastern part of the bay attracted terns in recent years, but minks devastated the birds. Some terns may return to Jenny Island, but may abandon the area if mink are still there.

“That’s why we want to be ready with Outer Green Island, so they would then see the decoys and hopefully settle in there,” said Stephen Kress, the director of the Outer Green Island project and other Audubon-managed seabird restoration projects in the Gulf of Maine.

Using decoys and sound recordings is not new. Kress and the Audubon Society pioneered the method with puffins in Maine, and the technique is now used in other areas.

“Everywhere we’ve tried it before, it’s worked,” Kress said. “Sometimes it takes years, but so far it’s always worked.”

Terns were once a common sight, but a growing gull population has crowded them out. Gulls nest earlier, are more aggressive and often destroy tern nests.

Outer Green Island was chosen for the project because of its location at the mouth of the Casco Bay, far from mainland predators. And, at two acres, it is larger than the other islands and has a place where a boat can land most days.

It’s not clear how long it will take for terns to find their way to Outer Green Island.