Montana Cooperative Wildlife Research Unit, University of Montana, United States
Abstract: Natural landscapes have been altered by human actions across the world, leading to widespread extinction and population declines in wildlife species. Recovery efforts have often focused on landscape management for umbrella species—vulnerable species whose conservation is thought to benefit co-occurring species. Sagebrush landscapes in North America represent an important example where landscapes have been degraded, resulting in drastic declines in wildlife populations. Large-scale encroachment of conifers into sagebrush landscapes has been widely documented to negatively impact Greater Sage-Grouse, and conifers are being removed to benefit sage-grouse as an umbrella species for the sagebrush biome. How this conservation action actually affects other species using sagebrush habitat is largely unknown. Here, we quantified the demographic effects of landscape-level conifer removal on a community of songbirds. We hypothesized that a species’ habitat association would be a useful surrogate to predict its demographic response. To test this, we quantified songbird density and reproduction between paired conifer removal and non-removal areas in southwest Montana. We conducted territory mapping to assess bird density and we located and monitored nests to assess reproduction. We found that sagebrush-obligate species benefitted from conifer removal through increased density, nest success and fledgling production. In fact, Sage Thrashers recolonized areas where conifers were removed. Woodland-associated species, including Chipping Sparrows, and Green-tailed Towhees showed the opposite pattern, while Dark-eyed Juncos were nearly extirpated from conifer removal areas. However, Green-tailed Towhees are of special concern because they are considered a near-obligate of sagebrush, while the other two woodland species are wide-ranging across North America. Between two shrubland generalist species, Vesper Sparrows were more abundant in removal areas, while White-crowned Sparrows were more abundant. However, these responses were aligned with their habitat associations, given that Vesper Sparrows are a grassland and shrubland associated species, but White-crowned Sparrows generally use shrubland and riparian areas. Our study demonstrates that habitat association may be a useful surrogate to predict species demographic response to umbrella species management. We saw that while some species will benefit, others are likely to be harmed. Better delineation of the demographic consequences of umbrella species management for co-occurring species can improve targeted conservation action.
