Most research on bird breeding site selection focuses on coarse characteristics of plant type and landscape structure at a variety of spatial scales. A broader approach would be to incorporate other factors (e.g., abundance of resources such as food) that might influence the presence and abundance of a given bird species at a particular site. However, there have been few comparisons of alternative factors that might limit bird populations. This study will test and compare three potential factors limiting the abundance of the Hawaiian moorhen, an endangered marsh bird: (1) local habitat structure and landscape features, (2) energy content and energy abundance of food plants, (3) and nutrient components of food plants. Moorhen abundance will be predicted using a suite of statistical models that will be compared to determine the most predictive relationships of abundance. Factors limiting the distribution and abundance of species are a central problem in ecology, and are poorly understood for most species, including birds. This will be only the second bird species for which such a wide suite of potentially limiting factors on abundance has been investigated. Results of this research also will provide important information for wetland managers in Hawaii on how to better manage this endangered species.
