Striking centennial-scale changes in the population size of a threatened seabird

Many animal populations are under stress and declining. For numerous marine bird species, only recent or sparse monitoring data are available, lacking the appropriate temporal perspective needed to consider natural, long-term population dynamics when developing conservation strategies. Here we use a combination of established paleoenvironmental approaches to examine the millennial-scale dynamics of the world’s largest colony (representing ~50% of the global population) of the declining and vulnerable Leach’s Storm-petrel (Hydrobates leucorhous). By reconstructing the last ~1,700 years of the colony’s population trends, we corroborate recent surveys indicating rapid declines since the 1980s. More surprisingly, however, was that population size was smaller and has changed strikingly in the past, even prior to the introduction of human stressors. Our results challenge notions that very large colonies are generally stable in the absence of anthropogenic pressures and speak to an increasingl...