Half the world’s breeding population of wandering albatrosses at risk after suspected deadly bird flu hits Marion Island

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Over 60,000 albatross chicks and adults have died in a suspected outbreak of avian influenza on a subantarctic island, a South African research team said on Tuesday, threatening nearly half the global breeding population of this critically endangered species.

The team, from the University of Cape Town’s FitzPatrick Institute of African Ornithology, visited subantarctic Marion Island from 1 - 26 August to investigate the mass mortality event that started in June, and confirmed the presence of the highly pathogenic H5N1 strain of avian influenza, commonly known as bird flu.

Half the world's 127,000 breeding wandering albatrosses nest on the small, remote island, located halfway between South Africa and Antarctica. The researchers estimated that more than 60,500 chicks and adults had died, or around 48% of the global population.

“This devastating event is a major concern,” said Peter Ryan, Fitzpatrick Institute director and one of the team leaders. “The mortality event is the largest ever recorded in a single albatross colony, and likely the largest recorded for any seabird population,” noted Ryan.

During this year’s breeding season, the team counted more than 26,000 dead chicks, with dead adult birds found under incubation nests, as well as 34,000 unhatched eggs abandoned by their incubating parents. Adult male albatrosses incubate the eggs for two months, before the females return for another two-month period. The unusual presence of males on nests with dead eggs indicates they were also affected by the virus.

Wandering albatrosses are long-lived birds that only start breeding at around 10 years of age, and can lay only one egg every two years. Each bird pair typically raises one chick every two to three years. The research team counted more than 13,000 nests and found many abandoned nests containing the bodies of adults sitting on eggs.

“The breeding failure for this year will have a significant impact on the species’ ability to recover. The loss of so many chicks represents the loss of a significant proportion of the potential next generation of the species. Similarly, the loss of more than 34,000 eggs is another huge setback,” said Chris Jones, a member of the team and a Distinguished Research Fellow in the FitzPatrick Institute.

The researchers believe the virus may have been spread to the island by other seabirds, such as white-chinned petrels or giant petrels, which still have mobile chicks that could have facilitated the spread of the virus. Preliminary genetic analysis suggests the virus is genetically closely related to viruses circulating more widely in southern Africa.

To prevent the spread of the virus to other islands and the mainland, the South African Department of Forestry, Fisheries and the Environment (DFFE) has established a restricted zone around Marion Island, and is monitoring movement in and out of the zone.

The research team is working with DFFE and the South African Centre for Epidemiological Modelling and Analysis to develop mathematical models that can help predict the future impact of the outbreak on the albatross population, and the necessary conservation interventions to help the species recover from this and future outbreaks.