Hufkens, KoenMeier, Christoph M.Evens, RubenParedes, Josefa AranKaraardic, HakanVercauteren, StefVan Gysel, Ann2026-01-242026-01-2420230962-84521471-2954https://doi.org/10.1098/rspb.2023.0957https://hdl.handle.net/20.500.12868/5055Recent studies have suggested the presence of moonlight mediated behaviour in avian aerial insectivores, such as swifts. Here, we use the combined analysis of state-of-the-art activity logger data across three swift species, the common, pallid and alpine swifts, to quantify flight height and activity in responses to moonlight-driven crepuscular and nocturnal light conditions. Our results show a significant response in flight heights to moonlight illuminance for common and pallid swifts, i.e. when moon illuminance increased flight height also increased, while a moonlight-driven response is absent in alpine swifts. We show a weak relationship between night-time illuminance-driven responses and twilight ascending behaviour, suggesting a decoupling of both crepuscular and night-time behaviour. We suggest that swifts optimize their flight behaviour to adapt to favourable night-time light conditions, driven by light-responsive and size-dependent vertical insect stratification and weather conditions.eninfo:eu-repo/semantics/openAccessmigrationresource and habitat useforagingflight altitudenight-time schedulelight pollutionArticle10.1098/rspb.2023.09572902010379090732-s2.0-85175679573Q1WOS:001096152000002Q1