eWestern Birds

Factors Influencing the Abundance and Distribution of the Snowy Plover at Mono Lake, California

W. David Shuford, Gary W. Page, Sacha K. Heath, and Kristie N. Nelson

ABSTRACT: The Snowy Plover is a species at risk, yet surveys of its numbers at most interior nesting sites in California have been infrequent. We surveyed the nesting population at one of the state’s key sites at Mono Lake at the edge of the Great Basin near Yosemite National Park in 6 years from 1978 to 2014. Diversions of inflowing streams caused the lake level to decline steadily from 1941 to 1981, increasing the amount of exposed lakebed available for nesting and foraging plovers. Subsequently, the level has generally risen, despite periodic reversals, since diversions were curtailed in 1989. Numbers of adult plovers at Mono Lake declined from 384 in 1978 to 71 in 2007, over a relatively narrow range of rising lake levels. In all years, plovers were distributed around the lake unevenly, with most on the northern and eastern shoreline. We found a positive relationship between the amount of exposed lakebed and the number of plovers detected on surveys. Plover numbers at Mono Lake may be limited by the amount and quality of alkali playa for nesting and foraging, low population density as an adaptation to high rates of nest predation, and perhaps by birds shifting to improved habitat at nearby Owens Lake. In coming years, provided the lake rises to the target elevation of 6392 feet (1948.3 m), the extent of the plover’s habitat will shrink, calling for more frequent monitoring.

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