Impacts of highly pathogenic avian influenza (HPAI) on a Barnacle Goose Branta leucopsis population wintering on the Solway Firth, UK

• Published in: Bird study Vol. 71; no. 4; pp. 392 - 403
• Main Authors: Griffin, Larry R., Peach, Will J.
• Format: Journal Article
• Language: English
• Published: Thetford Taylor & Francis 01.10.2024; British Trust for Ornithology
• Subjects: Animal breeding; Aquatic birds; Avian flu; Birds; Branta leucopsis; Breeding success; Carcasses; Collections; Estuaries; Estuarine dynamics; Mammals; Marine crustaceans; Mortality; Natural immunity; Outbreaks; Overwintering; Population; Scavenging; Sex; Waterfowl; Wildfowl
• ISSN: 0006-3657; 1944-6705
• DOI: 10.1080/00063657.2024.2443225

An outbreak of HPAI H5N1 amongst wintering Barnacle Geese in 2021/22 killed approximately 31% of the population (11,400 birds) with mortality peaking during December 2021 and first-year birds being under-represented in carcass collections. To describe the temporal progression and demographic impact of a major HPAI outbreak on a wintering population of wild geese. Long-term systematic abundance monitoring data were combined with carcass surveys and ringing data to quantify the impact of the HPAI outbreak on the wintering population. Comparison of carcass counts between fenced and unfenced fields provided an estimate of the extent of carcass removal by mammalian scavengers. Recoveries and re-sightings of ringed geese allowed us to test whether mortality was selective with respect to goose age, sex and breeding origin. Dead geese were first noted on the Solway Estuary in late October 2021 and mortality peaked during December and early January 2022, but declined to low levels by February. Counts of live geese declined by 31% (11,400 birds) between late November and February, which did not happen in preceding winters. Goose carcass counts on fields fenced to exclude larger mammals were 6.4 times greater than those on adjacent unfenced fields, suggesting high rates of carcass scavenging. Mortality appeared to be non-selective with respect to bird sex and breeding origin, and there was some evidence that first-year geese were under-represented in carcass samples. High breeding productivity in the two years following the HPAI outbreak coincided with a complete recovery of wintering goose numbers. The large impact of HPAI-related mortality on the Solway Barnacle Goose population was rapidly recovered, probably through a combination of the widespread development of natural immunity and high levels of breeding success in the years following the outbreak.