Sex, breeding status and spatiotemporal factors shape the movement of territorial Golden Eagles in Finland

Abstract

The rapid green transition has accelerated wind-energy development, increasing threats to large soaring raptors. Understanding key elements of movement behaviour—such as spatiotemporal variation in territory use that influences, for example, collision risk—is essential for reliable environmental impact assessment (EIA). We studied territorial movements of GPS-tagged Golden Eagles (Aquila chrysaetos; 11 males, 7 females) in central and northern Finland during 2011–2022. Using generalized linear mixed models, we evaluated the effects of sex, breeding status, month (March–October), and latitude on daily flight time and breeding-season territory size (core area and home range; 50% and 95% MCP, respectively). Flight time showed strong seasonality driven by sex and breeding status. Breeding males flew longer during incubation and the nestling period, whereas breeding females flew significantly less. Non-breeding birds showed weaker seasonal variation, consistent with the absence of parental care duties. Neither core-area size nor home-range size showed a statistically significant association with latitude, although MCP95 tended to decrease towards northern latitudes. Non-breeding females also tended to occupy larger home ranges than breeding females, whereas no corresponding difference was observed in males. Core areas tended to be larger in non-breeding than in breeding birds, and this pattern was most pronounced in females. Because flight activity and territory size depend strongly on individual characteristics and spatial context, we recommend that EIA monitoring covers multiple years, and that wind-energy guidance (e.g., buffer distances) is set conservatively based on individuals with the highest flight activity and/or the largest territories.