Determinants of Threatened Sage Grouse in Northeastern Nevada.

We examined potential human determinants of observed declines in greater sage grouse (Centrocercus urophasianus) populations in Elko County, Nevada. Although monitoring of sage grouse has occurred for decades, monitoring levels have not been consistent. This article contributes to the literature by normalizing grouse counts by the annual effort to count them, performing regression analyses to explain the resulting normalized data, and correcting for sample selectivity bias that arises from years when counts were not taken. Our findings provide some evidence that cattle-grazing contributes to a reduction in sage grouse populations, but this result should be interpreted with caution because our data do not include indications about the timing and precise nature of grazing practices. Annual variations in weather appear to be a major determinant after statistically controlling for human interactions with the landscape, suggesting that climate change is a key potential long-run threat to this species. [ABSTRACT FROM AUTHOR]