SCCF: Highest success for terns on causeway since 1990s
The Sanibel-Captiva Conservation Foundation (SCCF) reported that state-threatened least terns had a big success this year on the Sanibel Causeway Islands, producing more nests and chicks than they have in the location since at least the 1990s.
Black skimmers, which also historically nested on the causeway, also returned to nest.
At the peak of nesting, 142 least tern nests were being incubated, with 114 chicks in the colony.
“Nesting colonies are dynamic in nature, with new nests still being laid as older chicks are fledging and leaving the colony,” SCCF shorebird biologist Audrey Albrecht. “It is estimated that there were over 200 nests, fledging over 150 chicks. The earliest chicks fledged in May, and the last chick took flight on Aug. 2.”
About 30 black skimmers joined the least tern colony in mid-June. Although seven nests were documented, no chicks were ever confirmed.
HISTORY OF CAUSEWAY NESTING
Least terns and black skimmers regularly tried nesting on the Causeway Islands after the causeway was built in the 1960s. Unfortunately, vehicle traffic and summer storms left most nests unsuccessful.
“There are several newspaper articles detailing the struggles that least terns and black skimmers on the causeway historically faced from nest washovers and car strikes,” she said. “To the best of our knowledge, 2023 was the first time least terns had tried to nest on the causeway in at least 30 years, and 2025 is the most successful year since then.”
Albrecht reported that least terns likely returned to the causeway in 2023 due to the blank canvas of open sand created by Hurricane Ian reconstruction efforts.
Least terns are colonial nesters, meaning they nest in large groups as a strategy to protect eggs and deter predators. The migratory seabirds arrive to Southwest Florida in April and depart in August, and they require large, open areas to nest.
In 2024, least terns returned to the causeway once more, and that time successfully fledged at least 30 chicks. In 2023 and 2024, the SCCF worked closely with the Florida Department of Transportation and the Florida Fish and Wildlife Conservation Commission (FWC) to protect the colony and nests, while allowing essential restoration work to continue.
BIRDS NEST JUST AS PARK REOPENS
This year, SCCF biologists noticed least terns exhibiting nesting behavior on the causeway right before the Causeway Islands Park was set to open to the public for the first time in two and a half years.
“We immediately contacted FWC and Lee County staff to notify them of the nesting and worked together to rope off the nesting area in advance of the park’s opening on May 1,” Albrecht said. “Least tern eggs are extremely well camouflaged, making it vital to protect nesting areas from pedestrian and parking traffic.”
The SCCF also started a volunteer shorebird steward program to station education and outreach volunteers near the colony during peak weekend beach times.
Staff and more than 30 volunteers interacted with several hundred beachgoers throughout the season, offering information about the birds and a chance to view them up close with the spotting scope.
The SCCF thanked Trustee Kate Sergeant an On Island for providing the volunteer T-shirts.
“Without our partners, the support of our volunteers and the public’s interest in protecting these tiny birds, least terns would not have experienced the success we saw this season,” she said.