Waterbirds are an abundant, mobile, and highly sensitive group of animals dependent on some of the planet’s most threatened habitats.Their frequent movements link artificial and natural wetlands, and maintain metapopulation dynamics in fragmented landscapes. This talk reviews recent research on waterbird movement behavior, space use, and population dynamics in Hawaii and in Southern Spain. It begins with alandscape genetics analysis on the Hawaiian gallinule (Gallinula galeata sandvicensis), an endangered subspecies exhibiting strong genetic structuring over small spatial scales. Observed patterns of genetic dissimilarity strongly suggest that these birds rely on rivernetworks and other freshwater features to disperse across Oahu’s increasingly urbanized landscape. A subsequent spatially-explicit population viability analysis reveals that population fragmentation and sea level rise are a considerable threat to Oahu’s remaining gallinule populations. The final theme of the talk highlights preliminary data on the space-use of overwintering Lesser black-backed gulls (Larus fuscus), in artificial wetlands around Doñana National Park. Spatial analysis shows important shifts in space- and resource-use over the course of the winter season, with potential consequences for freshwater conservation and food safety.