Favorable winds speed up bird migration in spring but not in autumn

• Published in: Ecology and evolution 2022-08, Vol.12 (8), p.e9146-n/a
• Main Authors: Nussbaumer, Raphaël, Schmid, Baptiste, Bauer, Silke, Liechti, Felix
• Format: Article
• Language: English
• Subjects: aeroecology; Airspeed; Applied Ecology; Autumn; Behavioural Ecology; Bird migration; Energy; Energy consumption; Ground speed; Meteorological radar; movement; Movement Ecology; Radar; Radar data; season; Seasons; Spatial Ecology; Spring; Spring (season); Weather; weather radar; Wind; Wind speed
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.9146

Wind has a significant yet complex effect on bird migration speed. With prevailing south wind, overall migration is generally faster in spring than in autumn. However, studies on the difference in airspeed between seasons have shown contrasting results so far, in part due to their limited geographical or temporal coverage. Using the first full‐year weather radar data set of nocturnal bird migration across western Europe together with wind speed from reanalysis data, we investigate variation of airspeed across season. We additionally expand our analysis of ground speed, airspeed, wind speed, and wind profit variation across time (seasonal and daily) and space (geographical and altitudinal). Our result confirms that wind plays a major role in explaining both temporal and spatial variabilities in ground speed. The resulting airspeed remains relatively constant at all scales (daily, seasonal, geographically and altitudinally). We found that spring airspeed is overall 5% faster in Spring than autumn, but we argue that this number is not significant compared to the biases and limitation of weather radar data. The results of the analysis can be used to further investigate birds' migratory strategies across space and time, as well as their energy use. Using the first full year of weather radar data in western Europe, we investigate the difference of airspeed accros time (daily and seasonally) and space (geographically and altitudinal). Our result show that wind plays a major role in explaining the variation of groundspeed, while airspeed remains constant through space and time.