We collected data on mass mortality in Sandwich terns (Thalasseus sandvicensis) during the 2022 breeding season in the Netherlands. Mortality was associated with at least 2 variants of highly pathogenic avian influenza A(H5N1) virus clade 2.3.4.4b. We report on carcass removal efforts relative to survival in colonies. Mitigation strategies urgently require structured research.
Keywords: Charadriiformes; H5N1 subtype; Sandwich terns; Thalasseus sandvicensis; breeding; disease outbreaks; influenza; influenza A virus; influenza in birds; primary disease prevention; respiratory infections; seasons; the Netherlands; viruses; wild animals; zoonoses.