RT Journal Article SR Electronic T1 Modelling the flow of nocturnal bird migration with year-round European weather radar network JF bioRxiv FD Cold Spring Harbor Laboratory SP 2020.10.13.321844 DO 10.1101/2020.10.13.321844 A1 Nussbaumer, Raphäel A1 Benoit, Lionel A1 Mariethoz, Grégoire A1 Liechti, Felix A1 Bauer, Silke A1 Schmid, Baptiste YR 2020 UL http://biorxiv.org/content/early/2020/10/13/2020.10.13.321844.abstract AB The movements of migratory birds constitute huge biomass flows that influence ecosystems and human economy, agriculture and health through the transport of energy, nutrients, seeds, and parasites. To better understand the influence on ecosystems and the corresponding services and disservices, we need to characterize and quantify the movements of migratory birds at various spatial and temporal scales.Representing the flow of birds in the air as a fluid, we applied a flow model to interpolated maps of bird density and velocity retrieved from the European weather radar network, covering almost a full year. Using this model, we quantify how many birds take-off, flight and land each night across Europe. Cumulating these daily fluxes of take-off and landing over time, we can summarize the change in the number of birds on the ground over the seasons and the entire year, track waves of bird migration between nights across Europe, and identify regions that see major biomass movements.The resulting numbers are impressive: We estimate that during the breeding season, 187 million (M) more birds (623M arriving and 436M leaving) reside in Western Europe (than during winter), while 452 M more birds departed in autumn (934M leaving and 482M arriving).Our study show-cases the enormous potential of combining interdisciplinary data and methods to elucidate the dynamics of avian migration at various spatial and temporal scales, and once more emphasizes the importance of weather radar data being made available from all European countries.Competing Interest StatementThe authors have declared no competing interest.