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After 30 years, Least Terns Nest on Sanibel Causeway

June 16, 2023
protecting least tern nesting area on causeway

For the first time since 1993, least terns nested on the Sanibel Causeway Islands this season.

While the state-threatened birds haven’t recently been spotted, the fact they made an appearance shows that they are still here and seeking suitable nesting habitat.

Least terns on Bowman’s Beach in 2016.

This seabird species (Sternula antillarum) nests in colonies, preferably on open sandy areas like the Causeway Islands due to Hurricane Ian reconstruction.

“Our team watched carefully as they returned from their wintering grounds in Central and South America,” said SCCF Shorebird Biologist Audrey Albrecht. “In mid-May, we confirmed that least terns were in fact nesting on Causeway Island B.”

least terns by causeway
Look closely to see the least terns in the mid-bottom left of the image.

SCCF immediately notified staff from Lee County, the Florida Department of Transportation, and the Florida Fish and Wildlife Conservation Commission, who all jumped to action to ensure the terns would be monitored and protected while essential bridge repairs continue. Actions included marking off an enclosure around the nesting colony.

“As with all our beach-nesting wildlife, it’s important to respect posted areas and give them space. Flushing adult birds off their vulnerable eggs or chicks can leave them exposed to the elements and to predators,” Albrecht said. “Least terns always let you know when you are too close, as they will dive bomb and defecate upon any perceived threat.”

Historically, least terns and black skimmers (Rynchops niger) regularly attempted nesting on the Causeway Islands after it was built in the 1960s. Unfortunately, vehicle traffic and summer storms left most nests unsuccessful.

skimmers on causeway in 1980s
Black skimmers on the Causeway in the 1980s. Image by SCCF volunteer Al Milliken.

“Despite the best efforts of our local conservation organizations to protect them and lure them to other nesting sites away from the Causeway, the birds continued to fall victim to traffic and the weather,” Albrecht said. “They turned to other nearby beaches and rooftops but have struggled to find suitable nesting habitat in recent years.”

Least terns have a relatively short nesting season, arriving to Southwest Florida in early April and beginning their migration back to their wintering grounds in August.

Eggs incubate for three weeks, and chicks stay with parents for around five weeks as they develop and learn how to fish on their own. If their colony fails from weather, depredation, or other causes, they may relocate and attempt to nest again.

In addition to their return to the Causeway, the 2023 season has also seen the return of nesting least terns to the west end of Sanibel and Captiva for the first time in over a decade.

SCCF’s shorebird team works with partners and volunteers to monitor beach-nesting birds on North Captiva, Captiva, Sanibel, Bunche Beach, and the Sanibel Causeway.

Learn more about our shorebird program.


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