Habitat Relationships of Three Grassland Breeding Bird Species: Broadscale Comparisons and Hayfield Management Implications

摘要

Generalized recommendations for the conservation of birds in agro-ecosystems have been elusive because studies are often of a local nature, and do not compare source data against those from other regions. In this study, we developed geographically broad habitat relationship models to provide conservation prescriptions for three species that breed in farmed grasslands: Bobolink (Dolichonyx oryzivorus), Savannah Sparrow (Passerculus sandwichensis), and Nelson’s Sharp-tailed Sparrow (Ammodramus nelsoni subvirgatus). We develop models from our study in Nova Scotia, Canada and confront them with independent data from Wisconsin, USA pastures and Iowa, USA restored prairies. Vegetation that was higher and denser in the prebreeding season was linked to increased occupancy rates and abundance of Bobolinks in each study region. Providing tall spring grass is easily accomplished by not cutting late in the previous year. Savannah Sparrows were instead associated with shorter and sparser spring grass, which highlights the need to simultaneously provide heterogeneous habitat for otherwise ecologically similar species. Nelson’s Sharp-tailed Sparrows were more likely to occur, and be numerous, in areas with greater availability of drainage ditches. They and several other species would benefit from provision of ditches with adequate vegetation to promote occupancy. By combining these with other well-established recommendations, such as a delayed first harvest, a greater net conservation benefit can be realized from these working landscapes.