Distribution and ecology of the Hawaiian Moorhen

A long-term ecological problem is determining what influences species' abundances and distributions. Resolving this question for endangered species is important for improving management. My goal was to explore the ecology of the Hawaiian Moorhen (Gallinula chloropus sandvicensis) as they influence the species' distribution. First, I explored general questions of morphology, comparing Hawaiian Moorhen to other Common Moorhen subspecies. Adult Hawaiian Moorhen were similar to adults of other moorhen subspecies in size measurements, and there were no systematic differences between mainland and island subspecies. I also conducted call-broadcast surveys to improve population size estimates for moorhen. Results suggested that the population of moorhen in Hawaii is larger than previously thought but is still small and at risk. I also compared the call-broadcast approach with two other survey methods to determine which was most effective at improving population estimates, and call-broadcast performed the best. Additionally, I explored relationships between Hawaiian Moorhen numbers and habitat and landscape features at multiple spatial scales across two seasons. In this investigation I also analyzed the same relationships for Hawaiian Coots (Fulica alai) and Hawaiian Stilts (Himantopus mexicanus knudseni) because they co-occur with moorhen and have similar habitat requirements. Habitat relationships varied by season within and across species, and results confirmed some previous assumptions of waterbird-habitat relationships in Hawaii. I also explored whether energetic costs associated with reproduction and competition influence predictions of moorhen numbers. Results suggested that in areas supporting suitable wetland vegetation for breeding, Hawaiian Moorhen appear to have sufficient food resources from an energetic standpoint. Finally, I investigated molt patterns in moorhen because molt has the potential to influence habitat use. I caught molting and non-molting birds in the same habitat in which they breed. Hawaiian Moorhens typically molt all of their flight feathers and associated wing coverts simultaneously, rendering them vulnerable to predators during feather regrowth. This is consistent with patterns of flight feather molt reported for other Common Moorhen subspecies. Results from my research will help to inform needed management activities such as habitat management and wetland restoration. Improvement in management will help in the delisting process for this endangered species.