When the Mississippi and lower Ohio rivers drop to their normal summer pool at this time of year, the Endangered least tern shows up to nest on the exposed sand islands. Human disturbance can impact this nesting.
“Least terns are the only endangered species that nests in Kentucky,” said John Brunjes, migratory bird biologist for the Kentucky Department of Fish and Wildlife Resources. “They nest on isolated sandbars that are protected from predators and human disturbance.”
Brunjes explained most sandbars used by least terns for nesting in the state are located in the Mississippi River along the far western Kentucky border, and in the lower Ohio River from Paducah downstream to its confluence with the Mississippi, although they may nest as far east as Louisville.
“They like remote, vegetation-free sandbars for nesting,” Brunjes said. “If the islands grow up in vegetation – or there is too much human disturbance – then the least terns will abandon the island.”
Kentucky Fish and Wildlife employees mark nesting islands with signs, but that doesn’t always deter people from disturbing nests. “The problem is humans also like the same sandbars for swimming and camping,” Brunjes said. “They make a nice swimming spot. You feel like you are at the beach.”
Human activity causes least terns to flee the nest. That can expose the eggs to a killing heat. “The sand they nest in can reach 120 to 130 degrees on a hot summer day,” Brunjes said. “The adult is keeping the eggs protected from the sun’s heat.”
Brunjes also said wind can fill an unprotected least tern nest with sand in just a few minutes if the adults are not present. If river levels drop low enough to connect the island with the shore, potential human disturbance increases as people ride all-terrain vehicles on them, potentially destroying nests.
“Least terns build small nests which are so well camouflaged that a person can easily step on them,” Brunjes noted. “The nest, which holds three dime-sized eggs, is just a couple inches in diameter and one-half inch deep.”
Least tern chicks also blend in with their surroundings because of their sandy coloration. Their wariness of humans can be fatal. “When the chicks are on an island, they will run away from you and into the river,” Brunjes said. “The current will then take them away.”
Brunjes asks that river users respect the least tern nests and the work biologists are conducting to bring back this bird.
“We need people to respect this endangered bird by staying out of nesting areas,” he said. “If least terns are not on an island, go have fun. However, if you see our yellow signs, stay out.”
Law enforcement officers from the U.S. Fish and Wildlife Service and Kentucky Fish and Wildlife monitor least tern nesting sites. “Least terns are a protected species under federal law,” Brunjes said. “The fines for disobeying the Endangered Species Act are steep, up to $100,000. We have biologists out on the river every day along with monitoring by law enforcement.”
Brunjes said the monitoring works. “Last year, through concentrated effort, an island that had not had any least tern chicks on it for 30 years due to heavy human disturbance had over 200 chicks fledged on it,” he said. “They are one of our success stories.”