Lake Thompson is the largest lake in South Dakota that is not part of the Missouri  River reservoir system.
This site includes an open lake, cattail marshes, and CRP grasslands in public areas.  The lake is subject to fluctuating water levels.  Especially important is the fact that at times of low water levels, there are extensive mudflats that attract large numbers of migrating shorebirds. There are a significant number of dead and “drowned” trees in the lake which provide nesting habitat for waders and colonial waterbirds.

Ornithological Summary

The principal significance of this site is that under low water level conditions it is a major stopover for shorebirds. The lake also supports nesting waterbird colonies with up to six species of waders and colonial waterbirds (Great Blue Heron, Double-crested Cormorant, Great Egret, Snowy Egret, Cattle Egret, Black-crowned Night-heron).

Conservation Issues

Regarding shorebirds, if lake water levels are consistently high, suitable shorebird habitat will disappear.  Avian diversity will also decrease if row cropping agriculture increases. The watershed has a large amount of cropland which could cause nutrient pollution of the lake. In addition, the lake has some problems with sedimentation caused by soil erosion from cropland in the watershed.


This site contains a large lake and considerable state and federal public lands along the north, east, and south edges.



site includes an open lake, cattail marshes, and CRP grasslands in public areas.  The shorelines of the lake are mostly
treeless and are bordered by pastures and cropland.




Land Use

This site includes a lake and adjacent public lands, used primarily for recreation and wildlife production, and surrounding agricultural land.

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