Least terns nesting again on causeway
Least terns have returned to the Sanibel Causeway to nest for a second year in a row.
The Sanibel-Captiva Conservation Foundation reported that the state-threatened seabirds were found nesting on Causeway Island B last year for the first time in 30 years. This year, nesting activity has been observed on Causeway Island A and B.
“Least terns are colony nesters, meaning they nest in groups. This requires large open areas, including beaches, dry mudflats and gravel rooftops,” SCCF shorebird intern Riona Lahey said. “We’ve observed about 50 individuals on the causeway, across two different sites, with a handful of confirmed nests.”
The birds were seen during the first week of major rain this season in mid-June. After coordinating with the Florida Fish and Wildlife Conservation Commission and Florida Department of Transportation, the SCCF shorebird team posted the area during a rainstorm, providing a safe area for the least terns. The area was posted before eggs were laid, preventing any disturbance to actively nesting birds.
“Posted areas are important for beach-nesting birds like least terns to prevent harm from human disturbance, and in this case, harm from nesting in an active construction site,” she said, adding that monitors are on site during all construction activities to ensure no harm is done to the colonies.
Historically, least terns and black skimmers regularly attempted nesting on the causeway after it was built in the 1960s. Unfortunately, vehicle traffic and summer storms left most nests unsuccessful.
ABOUT LEAST TERNS
The SCCF reported that the least tern (Sternula antillarum) is the smallest tern species in the world, weighing in at just about 1.5 ounces. Along with their small size, adult least terns in breeding plumage can be easily identified by their bright yellow bill and legs, a black crown that extends over their eyes to form a white triangle on their forehead, and elegant narrow wings.
Their nests are known as “scrapes,” which are small nest bowls dug out in the sand where they lay their eggs. The incubation period for the eggs is about three weeks.
“Least tern chicks are known as altricial, which means chicks stay with their parents, relying on them for food and protection from the weather and predators. However, they’re not like most altricial chicks because they are downy at hatching and can move around freely, which is more of a precocial trait,” Lahey said. “The chicks stay with their parents for around five weeks until they develop flight feathers and are capable of foraging on their own.”
Least terns typically arrive on Sanibel in early April and depart by August. At the end of the breeding season they head to tropical waters, with some traveling as far south as Brazil.
The SCCF noted that as with all beach-nesting birds, it is important to respect posted areas and observe birds from a good distance. Flushing birds from their nest may leave their eggs vulnerable to predators and damage from the hot sun.
“Last year, the Sanibel Causeway nests unfortunately failed due to predation and over washing due to tides and low nest locations,” she said. “We hope that this season will be a successful one for these least terns.”