OMAHA, Neb. (AP) — The U.S. Army Corps of Engineers is reminding the public that some sandbars in the Missouri River between Nebraska and South Dakota are closed to recreational use to keep endangered bird species’ nests safe.

The Corps says endangered interior least terns and threatened piping plovers are currently nesting on sandbars around the Fort Randall Dam in South Dakota and Ponca State Park in Nebraska. The birds use the sandbars to lay their eggs and hatch chicks.

Corps Senior Program Manager Mark Harberg says closed sandbars are marked with signs warning the public to keep out of the area, but that some signs have been vandalized.

The nesting season runs from mid-May through August.