Thursday, August 9, 2007
Exhibit Halls 1 and 2, San Jose McEnery Convention Center
Livestock grazing is widely viewed as having negative effects on wildlife populations, but some species, under particular circumstances, may benefit from habitat conditions produced by grazing. Mountain Plover (Charadrius montanus) is a species of conservation concern in the western U.S. that nests in areas with short grasses and bare-ground patches. Cattle grazing may create preferred breeding habitat for plovers, but may also have indirect effects by altering the availability of insect prey or activity of nest predators. In 2003, we began a large-scale, replicated experiment to examine the responses of nesting birds (as a surrogate for Mountain Plovers), arthropods, and small mammals to five different treatments in an area of shortgrass steppe in northern Colorado. Treatments consisted of very intensive spring- and summer-cattle grazing, moderate summer grazing, black-tailed prairie dog colonies within moderately-grazed pastures, and long-term grazing exclosures. In the third year of our study (2006), we have begun to detect significant responses to treatments; our results suggest that heavily-grazed spring and summer treatments may create the most favorable conditions for Mountain Plover based on vegetation (short grass and shrub stature), nest predator (fewer), prey (more), and nesting bird (more Horned Lark nests) responses. To date, however, plovers only have been observed on prairie dog colonies, suggesting that these colonies are a valuable reference for the evaluation of grazing. If current trends in response variables persist, with additional sampling in subsequent years, we may continue to see positive effects of grazing on shortgrass steppe characteristics important to Mountain Plovers.