A newly published study has estimated that the global great black-backed gull population has almost halved within the past four decades.
Using the most recent population counts from across the species’ range, Sam Langlois Lopez and his colleagues analysed population trends at a global, continental, and national scale between 1985 and 2021.
Their results confirmed recent concerns among conservationists that great black-backed gull has been faring badly at both local and regional scales, with widespread declines noted across its North American and European range. The global population is estimated to have declined by up to 48% over the study period from an estimated 291,000 breeding pairs in 1985 to 152,000-165,000 breeding pairs in 2021.
The losses have been most pronounced in North American populations, where the species may have declined by up to 68% since 1985. Although faring comparatively better, European populations have still decreased by up to 28% over the same period.
While there were populations that showed growth between 1985 and 2021, these tended to be smaller and/or were present within a larger state or country where most populations declined. Most increases were recorded in populations on the periphery of great black-backed gull’s range, or in areas that have been recently colonised. These include Spain, Germany and The Netherlands in Europe, as well as North Carolina and Virginia in the US.
The reasons for the decrease are not clear, although are suspected in part to be related to a reduction in the availability of discards from the fishing industry, as well as an overall decline in food availability in the natural environment.
As a result of the findings, Langlois and his colleagues recommend that great black-backed gull should be uplisted from Least Concern to Vulnerable on the IUCN Red List of Threatened Species under criterion A2 (an estimated reduction in population size of more than 30% over three generations).
Read Global population and conservation status of the Great Black-backed Gull Larus marinus here