Status and population trends of Hawaii's native waterbirds, 1977-1987

Status and population trends of Hawaiis ’ native waterbirds were examined from 1977 through 1987. Waterbird population fluctuations were analyzed in relation to rainfall and land use dynamics. Numbers of Hawaiian Duck (Koloa) (Anus wyvilliana) and Hawaiian Common Moorhen (Gallinula chloropus sandvicensis) appeared stable over time; however, surveys were limited. Increase in Black-crowned Night-Heron (Nycticorux nycticorux) abundance appeared linked to expansion of aquaculture, particularly on Oahu, and not to climatic events. Annual rainfall patterns help explain and predict population fluctuations and anomalous distribution patterns involving Hawaiian American Coots (Fulica americana alai), moorhens, and Hawaiian Black-necked Stilts (Himantopus mexicanus knudseni). Coot, stilt, and moorhen populations fluctuated with climatic events, and intraisland dispersal to ephemeral wetlands occurred. Stilts exhibited regular inter-island migratory behavior, but coots dispersed in relation to major rainfall events. Seasonal fluctuation recorded for coots by past observers is the result of survey techniques not accounting for seasonal dispersal patterns.