Abstract Title
Effects of highly pathogenic avian influenza on the behavior and survival of Black-headed gulls during an outbreak in a breeding population in Sweden
Abstract
Since its emergence in 1996, the A/Goose/Guangdong/1/96 lineage of highly pathogenic avian influenza (HPAI) H5 virus has caused repeated outbreaks in wild birds, but the intensity and geographical scale of such outbreaks has intensified since 2021, with the spread of specific clade 2.3.4.4b genotypes. This change led to an expanded host range, with large-scale outbreaks in colonially breeding seabirds across Europe and North America, and later spread to South America and Antarctica. Among the most affected species in Europe is the black-headed gull (Chroicocephalus ridibundus), which experienced unprecedented mortality rates during the 2023 breeding season. While mortality is the most visible consequence, infection can also drive behavioral shifts with cascading effects on population dynamics. Studying such changes in the wild remains challenging during acute disease outbreaks. In this study, we monitored six black-headed gull colonies in Sweden, combining field observations and GPS tracking to examine HPAI’s epidemiological and behavioral impacts during the 2023 breeding season. Five colonies experienced outbreaks. We documented >90% juvenile mortality, leading to widespread nest abandonment, and 11 of 23 tagged birds in affected colonies estimated to have succumbed to disease. GPS data showed that infected colony birds traveled significantly shorter distances and altered migratory timing compared to the uninfected colony ones, suggesting potential energy deficits and disease-induced costs.
These findings underscore HPAI’s dual impact on mortality and behavior in this colonial species, with behavioral tracking providing key insight into sub-lethal effects that can improve epidemiological models and advance our understanding of HPAI’s impact on wild populations.
These findings underscore HPAI’s dual impact on mortality and behavior in this colonial species, with behavioral tracking providing key insight into sub-lethal effects that can improve epidemiological models and advance our understanding of HPAI’s impact on wild populations.
Co-Author(s)
Jonas Waldenström, Linnaeus University (Kalmar, Sweden)
Mariëlle Van Toor, Linnaeus University (Kalmar, Sweden)
Abstract Category
Notable outbreaks, field and molecular epidemiology, and surveillance in wild birds