This GPS tracking data set includes migratory trajectories of 70 adults lesser kestrels (Falco naumanni) (40 females and 30 males). These birds provided 75 post-breeding and 66 pre-breeding migratory trips. We re-sampled all data to 1-hourly intervals (with deviations of 20 minutes). After re-sampling, we analysed 31,012 hourly segments. Birds were captured on 33 breeding sites across Spain (n= 58) and Italy (n=12) between 2014 and 2019 by different teams: SEO/BirdLife Spain, GREFA, LIFE ZEPA-URBAN, KESTRELS-MOVE, LIFE+Natura project “Un falco per amico”. The data were used for the first PhD thesis chapter of Lina López Ricaurte Y-5977410-T, framed under the KESTRELS-MOVE project directed by Dr Javier Bustamante. This chapter was entitled “Barrier crossings and winds shape daily travel schedules and speeds of a flight generalist” and was published in Scientific Reports, June 8 2021, DOI: https://doi.org/10.1038/s41598-021-91378-x. It is recommended to use R software to read the data (also available on Movebank under the study name: (SP-IT) Lesser Kestrel migration). The data matrix contains the following fields: "LON"← longitude "LAT" ← latitude "ID” ← device code (6 characters) "HEIGHT" ← altitude (when available) "POP” ← country of origin, it/sp "sex" ← m/f "date” ← YYYY-MM-DD "season" ← spring/autumn "year" "cycle"← combination of “season” and “year” "daynight" ← day/night "desert" ← criterion for selectin positions over the desert, 1/NA "sea" ← criterion for selectin positions over the sea, 1/NA "date_time” ← YYYY-MM-DD HH-MIN-SEC "Vwind" ← v-component of the wind vector (positive values towards east, negative towards west) “BLH” ← proxy for the availability and strength of thermal uplifts "Uwind" ← u-component of the wind vector (positive values towards east, negative towards west) "trip” ← combination of “ID”, “year” and “season” (s1 = spring, s2 = autumn) "w" ← wind strength "alfa" ← wind direction (in degrees relative to north) "sidewind" ← km/h "tailwind" ← km/h "dis" ← the distance between point i and i-1 "duration" "speed" ← the speed between point i and i-1 "day2" ← bird-day from sunrise to sunset "migrate” ← classify travel days (> 5 km/h) and rest days (< 5 km/h) "barrier" ← classify barrier=1 vs non-barrier= 0 "cov.type" ← categorical variable with three levels to classify among Desert, Land, Sea.

External factors such as geography and weather strongly affect bird migration influencing daily travel schedules and flight speeds. For strictly thermal‑soaring migrants, weather explains most seasonal and regional differences in speed. Flight generalists, which alternate between soaring and flapping flight, are expected to be less dependent on weather, and daily travel schedules are likely to be strongly influenced by geography and internal factors such as sex. We GPS‑tracked the migration of 70 lesser kestrels (Falco naumanni) to estimate the relative importance of external factors (wind, geography), internal factors (sex) and season, and the extent to which they explain variation in travel speed, distance, and duration. Our results show that geography and tailwind are important factors in explaining variation in daily travel schedules and speeds. We found that wind explained most of the seasonal differences in travel speed. In both seasons, lesser kestrels sprinted across ecological barriers and frequently migrated during the day and night. Conversely, they travelled at a slower pace and mainly during the day over non‑barriers. Our results highlighted that external factors far outweighed internal factors and season in explaining variation in migratory behaviour of a flight generalist, despite its ability to switch between flight modes.

Peer reviewed