Factors Influencing Seasonal Migrations of Pronghorn Across the Northern Sagebrush Steppe

Abstract

Birds are a highly diverse group consisting of species that use a wide-range of available resources. Therefore bird communities are thought to represent the natural complexity of ecosystems. In recent years, groups of birds and individual species have been recognized as indicators of environmental change. Even with all the potential benefits of conserving bird populations, considerable declines of avian populations in the US have been well documented. These losses highlight the need for continued large-scale monitoring programs. The North American Breeding Bird Survey (BBS) and the Integrated Monitoring in Bird Conservation Regions (IMBCR) are independent large-scale programs conducted within the US to monitor populations of birds. Each of these programs is uniquely designed to provide different types of information to resource managers within the state of Montana. We examined the current products available from BBS and IMBCR programs and the methodology employed. We also compared how each monitoring program assesses population change at the Montana state level across a variety of species to investigate potential program inconsistencies. If programs work equivalently we would expect abundance trend estimates to be in the same direction (positive or negative) and of similar magnitudes. Preliminary results suggest 94% (104/111) of species analyzed exhibited some difference in their abundance trend estimates between monitoring programs. Inconsistencies found within our species comparisons reflect inherent differences in the programs. Our results reiterate the importance for users to carefully consider the unique design, intention, and sources of bias ascribed to each program before applying monitoring data to ecological questions.