Charadrius montanus: Montane, Grassland, or Bare-Ground Plover?

Abstract

The Mountain Plover (Charadrius montanus) is an aridland member of the Charadriidae. This plover is generally considered an associate of the North American shortgrass prairie, which is dominated by blue grama (Bouteloua gracilis) and buffalo grass (Buchloe dactyloides; Graul 1975). The species breeds at many locations across the western Great Plains plus at isolated locales in western Colorado, Wyoming, and New Mexico (Leachman and Osmundson 1990) and recently in eastern Utah (K. S. Day pers. comm.). Continental populations of the Mountain Plover declined 63% from 1966 to 1991 (Knopf 1994), with the historic and current breeding stronghold being the Pawnee National Grassland in Weld County, Colorado (Graul and Webster 1976). Currently, a second major breeding population of Mountain Plovers is on the Charles M. Russell National Wildlife Refuge, Phillips County, Montana. Unlike when found on the grassland landscape of Weld County, Mountain Plovers in Phillips County selectively nest in prairie dog (Cynomys spp.) towns (Knowles et al. 1982, Olson and Edge 1985) in vegetative settings that include prickly pear (Opuntia polyacantha), fringed sagewort (Artemisia frigida), big sagebrush (A. tridentata), western wheatgrass (Agropyron smithii), and blue grama. Collectively, Weld and Phillips counties provide nesting habitat for approximately one-half of the continental population of Mountain Plovers. Despite the differences in vegetation associations at the two major nesting locales, both Graul (1975) and Olson and Edge (1985) have described the tendency of plovers to place nests in areas of low herbaceous vegetation, reduced shrub cover, and near prominent objects such as cow-manure piles or similar-sized rocks. However, plover nests on Montana prairie dog towns also occur in areas of approximately 27% bare ground, a descriptor not mentioned by Graul (1975). The bare-ground variable may have some significance in light of recent findings of plovers sometimes nesting on plowed fields (Shackford 1991, pers. comm.) and descriptions of wintering habitats of plovers that mention use of freshly plowed ground in the San Joaquin and Imperial valleys of California (Grinnell and Miller 1944). We used a methodology similar to that employed in the Montana studies to ascertain if nest sites of Mountain Plovers also include a component of bare ground in native habitats on the