Modifications of fencelines and their effect on the Greater Sage-grouse


Greater sage-grouse (Centrocercus urophasianus) is a sagebrush obligate species of the American West. They require sagebrush during all stages of their life, from relying on open patches with nearby cover during the lekking season (breeding), to requiring areas with higher densities of sagebrush for nesting, to needing sagebrush during the winter as their main, and quite often, only food source. Adult survival can be relatively high for this species, accrediting the decline of many sage-grouse populations to the critical life stages of nesting and brood rearing. Most documented unsuccessful nests and broods can be attributed to predation. This predation is often facilitated through anthropogenic(human-related) structures and practices. Fencing is a common structure and practice throughout the range of greater sage-grouse and is widely undocumented on the affect it has on greater sage-grouse survival. Fencelines can create an edge effect that funnels predators (e.g. coyotes) along corridors due to their perceived impassability. They also create perches for avian predators (e.g. eagles, hawk species, ravens) that would otherwise be non-existent in the majority of the sagebrush ecosystem. Recent studies within the centennial valley have shown that sage-grouse nests placed near fencelines have lower survival rates than those nests places >100m away from fencelines. Based on this data, managers focused on survival and health of the greater sage-grouse populations within the centennial valley have implemented new techniques that modify fences with the intention of increasing the success rates of nests.
     Over the last 3 years, about 60km of fencelines have been modified in the sandhills region of the centennial valley. These modifications include the removal of the entire fence, the raising/ removal of the bottom wire, placement of perch deterrents (nixalite) on fenceposts, or a combination of the latter two. Biological technicians have been working throughout the summer collecting data on sage-grouse nest locations using radio telemetry equipment. They have been able to locate and monitor sage-grouse nests for their survival to test the effectiveness of these recent modifications. Since these modifications were put into place to reduce predator use along fencelines, it is important to assess the affects of this management plan on the predator community as well. To do so, our technicians have been using trail camera and point count methods to gain an index of both ground and aerial predator use along fencelines within the study area.
     The goals of this project are to a) determine the effectiveness of fence modifications on improving the survival of greater sage-grouse nests placed near fencelines, b) evaluate the perceived change in ground predator use of fencelines with the bottom wire removed, c) evaluate the perceived change in avian predator use patterns along fencelines modified with perch deterrents, d) assess how the changes in predator use along modified fencelines relates to the survival rates of sage-grouse nests. Answers to these questions will better inform management decisions regarding not only greater sage-grouse, but many other prey species being affected by the heightened rates of predation along fencelines. If proven effective, managers will have a new, relatively unobtrusive, tool to implement that can help increase the overall survival of greater sage-grouse.