Disentangling the influence of three major threats on the demography of an albatross community

Climate change, fisheries and invasive species represent three pervasive threats to seabirds, globally. Understanding the relative influence and compounding nature of marine and terrestrial threats on the demography of seabird communities is vital for evidence-based conservation.

Using 20 years of capture-mark-recapture data from four sympatric species of albatross (black-browed Thalassarche melanophris, grey-headed T. chrystostoma, light-mantled Phoebetria palpebrata and wandering Diomedea exulans) at subantarctic Macquarie Island, we quantified the temporal variability in survival, breeding probability and success. In three species (excluding the wandering albatross because of the small population), we also assessed the influence of fisheries, oceanographic and terrestrial change on these rates.

The Southern Annular Mode (SAM) explained 22.9-40.9% and 22.2-33.4% of the temporal variability in survival and breeding success respectively. Relationships were positive in all cases except between SAM and the breeding success of light-mantled albatrosses. The El Niño Southern Oscillation (ENSO) Index explained 24.9-43.1% of the variability in survival, with higher survival rates following La Niña events.

Habitat degradation caused by high density of rabbits Oryctolagus cuniculus explained 20.0-75.6% of the temporal variability in breeding probability, which declined in all three species. For black-browed albatrosses, effort in New Zealand trawl and south-west Atlantic longline fisheries had, respectively, positive and negative relationships with survival, and explained 21.2% and 22.3-31.6% of the variability.