Ranging Behavior of Non-Breeding and Breeding Adult White-Tailed Eagles

Abstract

Space utilization by animals is vital for species ecology but also a valuable predictor of habitat conditions and environment capacity for a given species. We investigated the ranging behavior of the white-tailed eagle, an apex predator experiencing a significant population increase and saturation. Comparing five adult floaters and two breeding males tracked with GPS loggers in Poland for 1–5 years, we observed substantial differences in space utilization. Breeding males occupied approximately 63 to 122 km2 (using 90% kernel density), while floaters ranged over roughly 6000 to 60,000 km2. Breeding males expanded their home ranges during successful breeding, with one male frequently flying 29 km to a foraging site when raising chicks but hardly doing so in other seasons. Both breeding males revisited nests more frequently in April and May (up to seven times daily, typically two to four), exhibiting distinct seasonal daily movement patterns. Floaters had slightly higher daily movement rates with a weak seasonal pattern. We conclude that breeding males’ ranging behavior depended on proximity to optimal foraging sites, while adult floaters engaged in prolonged wandering.

Keywords

• home range
• <i>Haliaeetus albicilla</i>
• GPS telemetry
• floaters