Birds on fire: severe disturbance by fireworks in wintering gulls, waterbirds and passerines

Fireworks are a global anthropogenic disturbance yet their impacts on wildlife remain poorly understood. Despite frequent media coverage and growing public concern about mass bird disturbances around New Year, scientifically robust assessments of nocturnal behavioural responses on the ground are lacking. Here, I quantified immediate and medium-term responses of urban birds, focusing on black-headed gulls, Chroicocephalus ridibundus , to New Year's Eve fireworks over three winters (2020/2021–2022/2023). For gulls, I recorded nocturnal flight time (proportion of time gulls spent flying) and disturbance behaviours (roost displacement, flocking responses and high-altitude flights). During New Year's Eve, immediate reactions included substantial increases in flight time and disturbance behaviours, particularly around midnight. Flight time was directly related to nearby fireworks, whereas disturbance behaviours remained elevated throughout the night, indicating cumulative stress-related effects. In the following days, gull abundance at the roost declined sharply, with disturbance behaviours remaining elevated. Full recovery took several days, indicating medium-term effects of stress. Waterbirds left the area after the first fireworks and did not return until the next day, while panicked flight responses of passerines were recorded, especially around midnight. The smallest behavioural disruptions occurred during the COVID-19 pandemic when firework usage was lowest. These findings demonstrate both short- and medium-term behavioural disruptions caused by fireworks, highlighting the need for mitigation measures to minimize impacts on wildlife.