Continental scale light-temperature extremes reveal key behavioural trade-offs

Daniel Gambra, Marta Peláez, Ramón Perea, Enrique Navarro, Birger Hornfeldt, Navinder J Singh

Daily rhythms determine ecological interactions, but we rarely know how animals convert activity schedules into movement and space use across extreme light–temperature regimes. Using multi-annual GPS data from 76 Golden Eagles (Aquila chrysaetos) tracked across Scandinavia and Iberia (spanning 35° latitude), we quantified diel activity and displacement to test how photoperiod and temperature reshape time budgets and movement. Activity was strongly diurnal with a midday peak, but its relationship with daylight was non-linear and latitude-specific: Scandinavian eagles shifted south in winter and remained active near freezing, whereas Iberian eagles were nomadic and reduced activity during long, hot days. Displacement peaks diverged from activity peaks, showing interactive light–temperature effects, greater movements by immatures, reduced movements during breeding, and winter maxima despite limited daylight. This partial decoupling reveals latitude-dependent movement–activity trade-offs: temperature alters the match between available active time and conditions for efficient travel, reshaping displacement and space use.