Signs, strung together and marked with bright orange flagging, have been installed around the perimeter of each nesting area to alert visitors to keep out. At Keewaydin Island, the shoreline remains open, and existing trails provide access across the island.

These nesting colonies are monitored to determine seasonal reproductive success and assess population trends. Protection of the colony early in the nesting season is the most important strategy employed to optimize success of the greatest number of nests, as well as survival of fledglings. This protection is critical, because as the season progresses, so does the chance of these areas being overwashed again by severe summer storms.

A combination of posting and closure, law enforcement presence, and education is necessary to maximize compliance by the public and enhance beach-nesting bird reproductive success. The Reserve will close and monitor these areas during least tern nesting season each year the terns are present as a continued effort to help protect this state-listed threatened species.



Least Tern Population

Least tern population estimates for Florida are around 10,000 individuals. Found only in the western hemisphere, least terns winter in Central and South America, arriving to nest and raise young on Florida beaches in late March.

Least terns are colonial, meaning they travel and nest together in groups. They have some very specific nesting requirements: wide sand and shell beaches with high enough elevations to avoid tidal overwash, sparse vegetation that provides shade but does not harbor predators, and minimal disturbance from human activity. Beaches that meet these requirements are fast disappearing from Florida’s coast.

Once an appropriate beach is located, least terns construct their nests by making a shallow depression scraped in the sand. With no apparent nesting material, tiny clusters of well-camouflaged eggs can easily be trampled by unwary beachgoers and their pets.

Adult least terns are very protective of their young, and attempt to ward off intruders by dive-bombing. When this occurs, the adult birds are expending valuable energy fending off perceived predators, leaving eggs or young vulnerable to heat exposure. Consistent disturbance often causes the nesting colony to fail.

Another threat to least tern nesting colonies is tidal overwash. Several areas locally that were once suitable for nesting have been reshaped over time and are no longer high enough or wide enough to sustain a colony. These changes can also occur overnight.

Coastal change events, such as extreme high tides or tropical storms, produce enough heavy surf and high tides to wash away scores of freshly laid eggs. This occurred at the Big Marco Pass colony earlier this year, and many of the terns were forced to re-nest. Many have relocated to adjacent beaches including Keewaydin Island.

Keewaydin Island is an unbridged barrier island within the boundaries of the Rookery Bay Reserve. Coastal processes over the past year have caused this area to become wider and the new beach is less vegetated. It now provides more suitable habitat than it has in previous years and the island currently hosts close to 100 nesting least terns. This area also serves as a popular recreation spot for boaters, fishing enthusiasts, beachcombers and campers, posing a greater challenge for land managers trying to balance the competition between wildlife and people for limited coastal resources.

least tern breeding biology