The Effects of Landscape Resistance on Inter-Wetland Movements of Hawaiian Stilts on Oahu.
Lello-Smith, Anna M.
- Abstract: Habitat fragmentation increases extinction risk by dividing populations into “islands” of smaller populations. By restricting movement across the landscape, habitat fragmentation can disrupt biological processes and threaten long-term population persistence. In the Hawaiian Islands, habitat loss and fragmentation have contributed to a high rate of avian species loss. Bird movement between ... read morewetlands is important for maintaining local populations. Habitat connectivity measures the ability of an animal in one habitat patch to reach other patches, and depends partly on “landscape resistance,” or the degree to which the landscape reduces the likelihood of movement between habitat patches. This study related observed inter-wetland movement patterns of Hawaiian stilts on Oahu to characteristics of the inter-wetland landscape in order to determine which characteristics impede bird movement. I hypothesized different levels of resistance for each of 4 landscape variables. I developed 4 models based on Euclidean distance and 108 models based on the 4 landscape features. For each hypothesis the landscape of Oahu was modeled as a GIS resistance surface. Each surface was evaluated to produce expected resistance distances between pairwise combinations of 10 wetlands on Oahu at which stilts were resighted. Expected resistance distances were compared to observed resistance distances derived from stilt resighting data. Elevation and landcover were the most influential landscape variables. Model explanatory power increased as the predicted resistance due to elevation increased. Both Euclidean distance and landscape variable models explained a significant amount of the variation in observed movement frequency among wetland pairs where movement was observed. Neither type of models predicted whether stilt movement occurred between wetlands. Occurrence or lack of movement may be influenced more by attributes of the wetlands themselves than by characteristics of the intervening landscape.read less