The common tern is a bird best known for its graceful flight and dramatic dives. The shoals and nooks of the eastern Lake Ontario and St. Lawrence River shoreline have been some of the tern’s best nesting habitat in North America.

But over the past 50 years, the area’s tern population has dropped dramatically, from 20,000 to only 2000. Now the tern’s a threatened species in New York.

A couple years ago, a biologist and some volunteers tried an experiment to create artificial nesting habitat for the terns, using little more than piles of gravel and the Seaway navigational markers that dot the river. David Sommerstein reports on the experiment’s progress.

Listen to story (6:46)