This 2016 video from the USA says about itself:
The Pennsylvania Game Commission conducted a camera trap survey in June 2016 to monitor common terns attempting to nest at Presque Isle State Park (PISP).
“Common Terns have been known to breed in Pennsylvania only in a small area at the east end of PISP. Although they were a fairly common nesting species in the early part of this century, there have been no successful nests since the mid-1960s. The breeding population quickly declined when their nesting area became a popular area for unrestricted swimming. Common Terns attempted to nest again after the long-overdue protection of this valuable ecological site in the mid-1990s. The breeding population has declined throughout the Great Lakes and the Atlantic coastal regions, owing in part to the same problems. … On 1 Jun 1930, Todd visited this site and counted at least 139 nests. In 1931 most nests were destroyed by bathers who walked among and even stepped on the eggs. … Common Terns are listed as Endangered by the Game Commission in Pennsylvania.”
Braining, Daniel W. and Gerald M. McWilliams. 2000. “The Birds of Pennsylvania”. Cornell University Press.
Based on the findings of these camera traps, the Game Commission may choose to try predator exclusion structures to help terns have a successful nesting colony.
From the Cornell Lab of Ornithology in the USA:
Do you have beachfront property or live near a beach? Our newest addition to our Right Bird, Right House interactive tool is a chick shelter for Common Terns! Nesting shelters are meant to protect chicks from avian predators such as owls and falcons, which commonly prey on tern colonies throughout their breeding range. The plans were provided by James McGarry of Save the River, an organization based at the St. Lawrence River in northern New York. Check out the plans now.