Piping Plover. Photo: Tom Grey

Populations of Interior Least Terns and Great Plains Piping Plovers are rebounding thanks to an Army Corps of Engineers effort to create sandbars on the Missouri River. These artificial breeding sites are helping offset habitat that has been lost due to flood control measures, which prevent the natural removal of vegetation from sandbars during high water events, leaving the birds with little of the bare sand they prefer.

The huge Missouri flood of 1997 removed most of the vegetation that had covered existing sandbars during decades of low flows, and created many new high-elevation sandbars that were suitable for successful nesting by the terns and plovers. This event reversed several years of worsening habitat trends, resulting in major increases in both tern and plover populations on the Missouri. These increases culminated in record counts for plovers in 2005 and terns in 2007.

Soon, however, many of these sandbars became recolonized by cottonwoods and willows, making many once again unsuitable as nesting sites. To offset these losses, the Army Corps of Engineers began mechanically creating sandbar habitat with dredges and bulldozers along a 58-mile stretch of river below Gavins Point Dam on the Nebraska-South Dakota border. The Corps created five sandbars, totaling 120 acres. By the 2006 breeding seasons, these five sandbars produced 74% of all plover fledglings, and 69% of all tern fledglings on the river reach below the dam. However, as the benefits of the 1997 flood dissipated due to erosion or vegetation growth, additional habitat creation became necessary.

Prior to the 2008 breeding season, the Corps created an additional 160 acres of high sandbar at three sites below Gavins Point Dam, and 80 acres of sandy islands on Lewis and Clark Lake. These new sites produced large numbers of successful tern nests and fledglings. Combining across all reaches of the Missouri River in 2008, 55% of all Least Tern fledglings and 28% of all Piping Plover fledglings came from sites created by the Corps.

“These are encouraging statistics given that, in the absence of regular large, habitat-forming flows, mechanical habitat creation will continue to be an important management strategy to provide nesting sandbars for terns and plovers,” said Casey Lott, American Bird Conservancy’s Coastal & Waterways Program Coordinator.