Print PageLoss of habitat is one of the primary factors affecting population declines of grassland birds, and recovery efforts have focused on increasing the amount of grassland habitat in the landscape. The type of planting used in grassland restorations influences both the structure and species composition of the vegetation, and the availability of arthropod food resources for breeding birds. We compared grassland bird habitat use and arthropod availability among restored grasslands planted with seed mixes of varying plant species diversity in the Spring Run Complex, Dickinson County, Iowa, USA in 2007, 2008, and 2009. We selected three grassland planting types, Cool Season, Warm Season (newly planted and mature), and High Diversity for our study to encompass the range of planting mixtures typically available to land managers. We sampled grassland bird densities using line transect surveys and arthropod abundance and biomass with sweep net sampling. We also evaluated vegetation structure and composition in each field.
Results/Conclusions
The most common bird species we encountered were Bobolink, Common Yellowthroat, Red-winged Blackbird, and Sedge Wren. Bobolink densities were higher in Cool Season fields than in any of the other field types in all three years. Common Yellowthroat densities in the first year of the study were highest in High Diversity and mature Warm Season fields, but did not differ among field types in subsequent years. Red-winged Blackbird densities did not differ among field types. Models of habitat use (vegetation structure and composition) varied by species, suggesting that variation in vegetation structure/composition should be preserved to provide habitat for this variety of grassland birds.
