Bird ‘flu devastates Welsh seabirds

Black-headed Gull (Bob Haycock)

The first estimate of the likely impact of Highly Pathogenic Avian Influenza (HPAI) on seabird populations in the UK shows big changes even before last year’s outbreaks. The RSPB Centre for Conservation Science compared numbers in spring 2023 to surveys at the same colonies during 2015-21. The report estimates the impact of HPAI in the 2022 breeding season and the following winter, when seabirds are in the Atlantic Ocean, some as far away as southern Africa. The biggest population changes were in species that tested positive for HPAI across multiple colonies in northwest Europe.

In Wales, the most substantial effects were on Black-headed Gull, which was already on the Welsh Red-list of conservation concern having suffered huge declines between 1973 and 2000, when many inland colonies were abandoned completely. This new assessment, at three-quarters of remaining Welsh sites, showed a further 77% decline. In total, the population has fallen by around 95% in 50 years.

Counts of breeding seabirds in Wales in 2023 compared to baseline (2015-21), compiled from RSPB Research Report no.76

Gannet, Common Tern and Sandwich Tern were also badly affected in Wales, as shown in the table above. Detailed monitoring by reserve wardens shows that numbers of Gannets on Grassholm, which was the fourth largest colony in the world, fell by 52% in just one year between 2022 and ’23. The number of Sandwich Terns nesting at Cemlyn, Anglesey, fell by around 50% in the same period, and of Common Terns at four colonies by 28% in just one year. It doesn’t account for the further effects of HPAI in summer 2023, when adults and chicks died at the most important gull and tern colonies in Wales.
​
The wider effects of bird flu are evident in counts of Great Skuas migrating past Wales. The Welsh Bird Report showed that numbers in autumn 2022 were 87% below average. The following summer, the Scottish breeding population was 76% lower. 

Counts of Great Skua passing the Welsh coast, 2001-22. Data courtesy of Welsh Ornithological Society.

Guillemots, Shags and Fulmars are starting to return to their cliff ledges, but it will be May before wardens at seabird colonies get a feel for numbers, and all will fear a repeat of last summer’s ghastly scenes of sick and dying seabirds. Even if bird ‘flu is minimal this year, recovery will be slow because it takes several years for birds to mature to breeding age. It may be the end of the decade before the full consequences are realised. RSPB Cymru is calling on Welsh Government to complete its promised Seabird Conservation Strategy and commit funding to actions that will increase resilience to other pressures in the marine environment, making them better able to face sudden shocks such as disease. Even before HPAI, the UK’s seabirds were under pressure from climate change, industrial fishing, invasive non-native animals and offshore energy infrastructure.
​
Winter visitors to our coast this week include two Surf and up to 12 Velvet Scoters at Llanddulas, Black-necked and Slavonian Grebes off Aber Ogwen and Borth-y-gest. In Flintshire, a flock of 150 Waxwings remains above Pentre Halkyn, 25 Twite at Flint Castle, six Snow Buntings at RSPB Point of Ayr and three at Gronant. A Ring-necked Duck and four Scaup are on Llyn Tegid, and a Dipper is already nest-building on the river at Rossett.