A Landscape Analysis of Grassland Birds in a Valley Grassland-Oak Woodland Mosaic

While little research has been done on California grassland birds, their populations are thought to be declining due to habitat loss, fragmentation, and degradation. We investigated the association between California grassland birds and their landscape-scale habitat matrix. The habitat is a mosaic of valley grassland with blue oak and coast live oak woodlands. In this study, we used logistic regression to analyze presence of grasshopper sparrows (Ammodramus savannarum), horned larks (Eremophila alpestris), western meadowlarks (Sturnella neglecta), savannah sparrows (Passerculus sandwichensis), and the guild as a whole in response to patch size, cover-type richness, and proportion of high-intensity development, low-intensity development, deciduous forest, and evergreen forest in the landscape. These landscape variables were analyzed for the 2004 and 2005 breeding seasons at three spatial scales: 500 m, 1 km, and 2 km buffer zones from the point count center. We found that the grassland bird guild as a whole was positively associated with patch size, proportion of low-intensity development, and proportion of evergreen forest and negatively associated with cover-type richness, proportion of high-intensity development, and proportion of deciduous forest. Patch size and cover-type richness were the most commonly significant variables across spatial scales and across years. Individual species showed similar trends to that of the guild.