Nocturnal bird migration across western Europe

Continuous, high resolution spatio-temporal maps of nocturnal bird migration densities, flight speed in east(+)/west(-) direction (u component) and flight speed in north(+)/south(-) direction (v component) across western Europe were interpolated from vertical profile time series datasets measured by 37 weather radars in France, Germany, The Netherlands and Belgium operating between 13 February 2018 and 1 January 2019. Each raster represents a nightly average and represents data collected on 2 dates, e.g., the file called “2018-02-14_u_est” was calculated from data collected starting at sunset on 13 Feb through sunrise on 14 Feb. The approach used in this study models bird flow (i.e. average bird movement) of long- and short-distant nocturnal migrants on a nightly time scale and regional/continental spatial scale. The speed of individual birds is typically higher than the speed of the overall flow, and the flight directions of individual birds are more variable than the overall flow direction. Similarly, the modelled flow is unable to track separately multiple bird populations simultaneously migrating in different directions (Nussbaumer, R., et al., 2021, Quantifying year-round nocturnal bird migration with a fluid dynamics model).