Landscape and local factors affecting the use of native and planted grasslands by Sprague's pipits

Sprague's pipit (Anthus spragueii) is a small songbird that typically breeds in grazed, native grasslands (i.e., fields undisturbed by humans), yet they have been observed nesting in fields planted with exotic grass and forb species (hereafter "planted grassland"). I used a comparative approach over multiple spatial and temporal scales to address two objectives: (1) determine under what conditions (landscape context, local patch characteristics, vegetation structure) pipits use planted grasslands, and (2) determine whether planted grasslands offer similar habitat for pipits compared to native grasslands. Not surprisingly, pipit abundance was almost twice as high in native grasslands compared to planted grasslands. However, pipit abundance in both these habitat types increased as the amount of native grassland in the landscape increased. In planted grasslands, pipits used territories with 25 cm vegetation height, which was intermediate compared to available vegetation height. In native grasslands, pipits used territories with heterogeneous bare ground exposure compared to random areas, but territories contained on average 15% bare ground. Pipits nested in areas with 25- 30 cm vegetation height in both habitats. I postulate that the vegetation structure used by pipits within territories and at nests in both habitat types reflects a tradeoff among access to resources, cover from predators, suitable microclimate, and predator detection. Dispersal distance of juveniles was greater in planted compared to native grasslands, but appeared to be constrained to natal fields up to 26-d post-fledging. Juvenile pipits used microhabitats in planted grasslands with vegetation that was on average 11 cm taller than at the locations used in native grasslands, possibly due to the greater height of planted vegetation by the time individuals fledged. Juveniles that were reared in planted grasslands had consistently lower daily survival rates compared to those reared in native grasslands. Conservation of native grasslands with already established pipit populations, in addition to acquiring and conserving native grasslands surrounding these native grasslands, appears to be the best conservation strategy for pipits. Although pipits used planted grasslands, the lower survival rate of juveniles in this habitat compared to juveniles reared in native grasslands suggests these planted grasslands may be acting as population sinks.