Highly pathogenic avian influenza H5N1 has caused unprecedented mortality in wild seabird populations since 2021, representing a major wildlife welfare crisis with ongoing implications.
H5N1 avian influenza causes acute neurological suffering followed by death in most affected birds. The rapid progression from initial symptoms to death compresses the welfare impact into hours to days, but the neurological symptoms - circling, head tremors, inability to balance - indicate significant distress. At colony scale, mass mortality events cause secondary welfare impacts: nesting partners whose mates die face breeding failure; chicks surviving parental death face starvation. The long-term population impacts of losing entire breeding seasons at critical seabird colonies will compound through reduced recruitment for years. Sick birds found by the public should not be handled without PPE due to zoonotic risk.