Habitat associations and conservation of wetland-obligate birds

Abstract

A basic understanding of species-specific habitat associations is a prerequisite for the effective management of at-risk species. Many wetland-dependent birds in the Upper Midwest are at-risk due to habitat loss and degradation. To investigate the habitat associations of wetland-dependent birds, I: 1) determine the relative importance of habitat heterogeneity vs. wetland area for biodiversity and species abundance, 2) develop species-specific models of habitat associations for eight declining obligate wetland bird species that use coastal wetland habitat in the Great Lakes basin, and 3) provide general habitat models for these species that are useful across multiple regions. The central hypothesis of this work is that populations of wetland-dependent birds are influenced by a combination of landscape and proximate habitat features, regionally specific hydrologic conditions, and anthropogenic stressors. Findings from the analysis of habitat heterogeneity indicated support for a tradeoff between area and habitat heterogeneity but highlight the importance of wetland area as the primary driver of variation in species richness and abundance. Species-specific combinations of habitat heterogeneity and other wetland characteristics provided additional explanatory power. Findings from hierarchical multi-scale occupancy models for coastal wetland birds in the Great Lakes basin indicated that the eight focal species are eurytopic, with little variation in occupancy despite differences in remotely sensed landscape characteristics, including anthropogenic disturbance. These species use a high proportion of the coastal wetlands in at least some years. Thus, wetland loss is problematic for these species and conservation planning should focus on protecting as many wetlands as possible. Finally, the regional comparison showed that these species have regionally specific habitat associations, but in most cases, associations estimated in one region can be informative when applied to other regions. In conclusion, habitat associations of wetland birds in the Upper Midwest are both species- and region-specific. Conservation of these species will depend primarily on protecting wetlands across a gradient of habitat characteristics at multiple scales and on reversing ongoing trends of wetland loss.