Highly pathogenic avian influenza H5N1 caused mass mortality of wildlife across the North Atlantic in 2022. Following European outbreaks, the first North American case was detected on the island of Newfoundland, Canada in November 2021, before spreading throughout North America. During the following summer, Newfoundland and surrounding islands (NFLD) experienced one of the most significant mortalities in Canadian provinces, with seabirds being the most affected taxa. From surveys and citizen reports, we estimate that 13517 mortalities that can be attributed to HPAI occurred in NFLD from April to September 2022. Most estimated mortalities were among Northern Gannets (Morus bassanus, Linnaeus, 1758) (6596), Common Murres (Uria aalge, Pontoppidan, 1763) (5992), Atlantic Puffins (Fratercula arctica, Linnaeus, 1758) (282), and Black-legged Kittiwakes (Rissa tridactyla, Linnaeus, 1758) (217). Mortality reports moved from west to east along the southern then eastern NFLD coast and peaked in July and August. We formulated exploratory hypotheses regarding traits that could contribute to infection and mortality. Species differences in mortality most strongly associated with inter-nest distance, breeding phenology, and at-sea overlap with allospecifics from other colonies. Unprecedented seabird mortality and ongoing transmission within the circulating avian influenza viruses highlight the need for continued monitoring and development of conservation strategies.

Gretchen M. McPhail1, Sydney M. Collins2, Tori V. Burt2, Noah G. Careen3, Parker B. Doiron2, Stephanie Avery-Gomm4, Tatsiana Barychka4, Matthew D. English5, Jolene A. Giacinti4, Megan E.B. Jones6,7, Jennifer F. Provencher4, Catherine Soos8, Christopher R.E. Ward9, Steven Duffy10, Sabina I. Wilhelm9, Jordan Wight1, Ishraq Rahman1, Kathryn E. Hargan1, Andrew S. Lang1, William A. Montevecchi3* 1 Memorial University of Newfoundland and Labrador, Department of Biology, St. John’s, Newfoundland and Labrador, Canada 2 Memorial University of Newfoundland and Labrador, Cognitive and Behavioural Ecology Program, Departments of Psychology and Biology, St. John’s, Newfoundland and Labrador, Canada 3 Memorial University of Newfoundland and Labrador, Department of Psychology, St. John’s, Newfoundland and Labrador, Canada 4 Environment and Climate Change Canada, Wildlife and Landscape Science Directorate, Ottawa, Ontario, Canada 5 Environment and Climate Change Canada, Canadian Wildlife Service, Dartmouth, Nova Scotia, Canada 6 University of Prince Edward Island, Department of Pathology and Microbiology, Charlottetown, Prince Edward Island, Canada 7 Canadian Wildlife Health Cooperative, Charlottetown, Prince Edward Island, Canada 8 Environment and Climate Change Canada, Wildlife and Landscape Science Directorate, Saskatoon, Saskatchewan, Canada 9 Environment and Climate Change Canada, Canadian Wildlife Service, Mount Pearl, Newfoundland and Labrador, Canada 10 Fisheries and Oceans Canada, Northwest Atlantic Fisheries Centre, St. John’s, Newfoundland and Labrador, Canada

Mortality estimations, impacts on harvest, conservation considerations, and potential mitigation strategies in wild birds