Demographic responses to environmental change of the black-browed albatross, sentinel of the Patagonian Shelf Large Marine Ecosystem

Abstract

In long-lived marine top-predators with delayed sexual maturity such as seabirds, adult survival is predicted to drive population dynamics. Major knowledge gaps exist for the cryptic sub-adult stages of the population. Yet as the oceans undergo dramatic change, investigating the trends of top-predator populations and their responses to environmental variability is key for a process-based understanding of climate change. Using integrated population models based on a longitudinal data set spanning nearly 2 decades, we investigated the demographic rates and environmental drivers shaping the dynamics of a longevous marine top-predator population, the black-browed albatross Thalassarche melanophris in the Falklands. We quantified the dynamics of the whole population, including its cryptic sub-adult stages, and examined the effects of candidate environmental covariates on adult survival and productivity parameters. We found that high survival rates of both adults and juveniles are the main contributors to the growth of this albatross population, the only one that is increasing in the South Atlantic. The breeding parameters were affected by environmental fluctuations through bottom-up processes, with a negative effect of higher sea surface temperatures and a positive effect of wind intensity. The relatively constant adult survival was influenced by deeper ecosystem changes, captured by large-scale indices (Southern Annular Mode). Approximately half of the total population is composed of sub-adults, and the population dynamics are highly sensitive to changes in juvenile survival; addressing current knowledge gaps in these cryptic life-history stages is therefore a conservation goal of primary importance.