Study area and study species
The study was conducted within the red kite breeding period (March to July), during the years 2016 to 2018 in the cantons of Fribourg and Bern, Switzerland (46°5´N, 7´15°E). The study area has an extent of approximately 17.5 x 22.5 km (c. 394 km2), covers elevations from 530 - 1500 m a.s.l., and is characterized by agriculture (56.25%) and managed forests (26.95%) interspersed with settlements. The agriculture is dominated by dairy farming and meat production, resulting in large areas dominated by grassland(Nägeli et al. 2022; Scherler et al. 2023b; Welti et al. 2020). The red kite is a facultatively scavenging European raptor species that also profits from anthropogenic feeding (Cereghetti et al. 2019; Orros and Fellowes 2015) and builds nests in forest patches, tree rows or single trees (Aebischer and Scherler 2021). The well-known study population shows a very high density of c. 30 pairs per 100 km2(Aebischer and Scherler 2021; Knaus et al. 2018). Egg laying occurs mostly at the beginning of April and clutch size is 2.57 ± 0.62 eggs (range 1 - 4; Scherler et al. 2023a). Brood survival and survival of nestlings depend on weather conditions and food availability (Nägeli et al. 2022). After hatching, parental attendance at the nest declines continuously throughout the nestling period and Carrion crows (Corvus corone), Northern Goshawk (Accipiter gentilis), and Eagle Owls (Bubo bubo) represent the most common avian nest predators (Scherler et al. 2023a).