Associated Press - September 12, 2009 1:34 PM ET

SIOUX FALLS, S.D. (AP) - Reproduction of 2 endangered birds on the Missouri River system took a dive this summer.

The Army Corps of Engineers is required to provide nesting habitat for piping plovers (PLOH'-vers) and least terns. It monitors their populations and nesting success.

Some shoreline habitat vanished when Lakes Oahe and Sakakawea (suh-kah-kuh-WEE'-uh) filled this year. Thunderstorms also killed chicks on sandbars below Yankton.

A final count showed 425 plover chicks and 278 tern chicks survived. Plover reproduction was down 37% from last year. Tern reproduction fell 28%.

The birds have already gone south for winter.

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