Birds on Fire: Heavy disturbance by fireworks affecting wintering gulls, waterbirds and passerines

Valentin Moser

Fireworks are a global anthropogenic disturbance, yet their impacts on wildlife remain poorly understood. Despite frequent media coverage and growing public concern of mass bird disturbances around New Year, scientifically robust assessments of nocturnal behavioural responses on the ground are lacking. Here, I quantified immediate and mid-term responses of urban birds with a focus on Black-headed Gulls (Chroicocephalus ridibundus) to New Year’s Eve fireworks over three winters (2020/21–2022/23). For gulls, I recorded nocturnal flight time (proportion of time gulls spent flying) and disturbance behaviours (roost displacement, flocking responses, 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 effects. In the following days, gull abundance at the roost first declined sharply (17–62%) with disturbance behaviours remaining elevated. Full recovery took several days, indicating mid-term impacts of stress. Waterbirds left the area after the first fireworks until the next day, while panicked flight reactions 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 mid-term behavioural disruptions caused by fireworks, highlighting the need for mitigation measures to minimise impacts on wildlife.