Wave of avian influenza hitting Black-headed Gulls
Wave of avian influenza hitting Black-headed Gulls16 May 2023
Avian Influenza is killing large numbers of Black-headed Gulls at inland and coastal breeding colonies across central and northern England, prompting fears among scientists that a new wave of the disease could be building.
As many as a thousand Black-headed Gulls are thought to have been killed by Avian Influenza at Marsh Lane Nature Reserve near Coventry, while around 800 are feared to have died at RSPB St Aidans, near Leeds, and around 250 at Rutland Water. The majority of sick or dying Black-headed Gulls confirmed to have Avian Influenza have been reported from sites between Buckinghamshire and Yorkshire, with cases also reported in Surrey and Montgomeryshire.
Although only a relatively small number of dead birds are tested for Avian Influenza, current sampling suggests very large numbers of Black-headed Gulls are likely to be affected. All dead birds of any species should be reported to BirdTrack, which allows researchers to follow the disease’s geographical spread, and to Defra, which will decide if a particular case reaches the threshold for testing. These sources indicate that more than 4,000 Black-headed Gulls have died in just the past few weeks, and that the mortality rate is increasing.
This figure already represents 1% of the 140,000 pairs of Black-headed Gull thought to breed in the UK each year. Worryingly, the breeding population has already been in decline for a number of years, and the species was placed on the Amber List of Birds of Conservation Concern in 2021. The impact Avian Influenza will have on this already struggling species remains unclear, but if the current rate of mortality continues it has the potential to have a large impact on this familiar and charismatic species. Black-headed Gulls nest alongside other species, such as Common Tern, Sandwich Tern and Avocet: there are concerns that these too might be affected.
Similar mortalities among Black-headed Gulls were reported in France earlier this year, followed by birds in the Low Countries, Italy and Germany. Data from bird ringing show that Black-headed Gulls that breed in the UK often spend the winter in western continental Europe before migrating north, indicating a possible route of transmission. If the loss of breeding Black-headed Gulls is replicated across Europe, which seems likely, this could be the next chapter in the impact that this already catastrophic disease has had on European breeding seabirds, and would be likely to significantly reduce the number of wintering birds that return to the UK next autumn and winter.
Members of the public are reminded not to pick up dead birds and to keep dogs on leads to prevent them from scavenging on carcasses.
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