Fig. 1

Nest boxes containing different types of nest material occupied by the European Kestrel. Nest materials were categorized into seven types based on previous breeders and manipulation treatments in the study: without nest material (WNM), old European Kestrel nest material (EKM), Great Tit nest material (GTM, both new and old), old Eurasian Red Squirrel nest material (ERSM), artificial nest material of dry leaves and branches (ANM), simulated Eurasian Red Squirrel nest material (SESM), and other types of nest material (OTM, mainly including old Mandarin Duck and Ural Owl nest materials)