Mormon Reservoir is an irrigation reservoir on Camas Prairie in Southwest Camas County. The reservoir is mostly open water with significant mudflats at the southern end, during late summer and low water years. There are two islands in the reservoir, one of which is fairly flat with no vegetation and is used by nesting gulls. The mudflats and surrounding perennial vegetation at the south end provide ideal nesting habitat for shorebirds.

Ornithological Summary

Thousands of breeding pairs of California and Ring-billed Gulls have historically used this site. In 1993, there were over 11,000 pairs of gulls breeding here (8,000 CAGU; 3,600 RBGU). In recent drought years, the number of breeding pairs has decreased significantly, but will likely rebound once the reservoir returns to normal water levels. This site also attracts numerous breeding and migrating shorebirds. American Avocets, Killdeer, Willets, Wilson?s Phalarope, and Black-necked Stilts likely breed here. Other shorebirds, including Least Sandpipers, Marbled Godwits, and Dowitchers use this site during migration. Large numbers of Sandhill Cranes also use this site as a staging area in late summer.

Conservation Issues

This is an irrigation reservoir subject to extreme drawdown and drought. Predation of nests is likely a problem during drought/low water events. During recent droughts, the number of nesting gulls has plummeted, and no birds successfully bred in 2004 or 2005. However, the reservoir filled to capacity again in 2006, and nesting gulls have returned. Grazing on adjacent lands also could aversely affect breeding birds.

Habitat

The reservoir is mostly open water with significant mudflats at the southern end, during late summer and low water years. There are two islands in the reservoir, one of which is fairly flat with no vegetation. This island is used by nesting gulls. The mudflats and surrounding perennial vegetation at the south end provide ideal nesting habitat for shorebirds.

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