Replacement clutch of greater Spotted Eagle Clanga clanga after clutch loss: the first documented case in Poland

Re-nesting within the same breeding season after clutch loss is very rarely observed in large raptors, including the endangered greater Spotted Eagle (Clanga clanga). Here, we describe the first well-documented and confirmed case of clutch replacement in this species, observed in 2024 in the Biebrza Basin (NE Poland). Using modern telemetry, camera trapping technologies, and individual marking, we tracked an adult female that abandoned her first clutch due to disturbance caused by a swarm of insects. After an energy-replenishing period of abundant foraging, the female re-nested with the same male had previously bred with and successfully raised a chick in a different nest. This unprecedented event in this species underscores how the combination of early clutch replacement, sufficient food resources, and nest availability can enable re-nesting, and how such conditions may be relevant for the conservation of this threatened species.