Trends in numbers and survival of Black-browed (Thalassarche melanophrys) and Grey-headed (T. chrysostoma) Albatrosses breeding on Macquarie Island

Abstract

Black-browed (Thalassarche melanophrys) and Grey-headed (T. chrysostoma) Albatrosses are globally threatened seabirds that breed on remote subantarctic islands. Population trends of Black-browed and Grey-headed Albatrosses breeding on Macquarie Island were described using historical data combined with data from a more intensive 10-year monitoring program. Survival estimates were also calculated for both species over similar time frames. Breeding numbers and survival rates of Black-browed and Grey-headed Albatrosses appear to have remained stable since the mid-1970s. There was no conclusive evidence of survival varying over time and it is unlikely that mortality owing to fisheries’ activities has had a significant impact on these populations. This is in contrast to most other subantarctic populations of these species and may be attributed to their foraging ranges not overlapping significantly with areas of high fishing effort. However, both species forage in areas of new and expanding legal and illegal fishery operations. Owing to their extremely small size, these populations remain chronically vulnerable to any elevated levels of mortality.