Influence of habitat characteristics on the concentrations of metals and other elements in a sedentary terrestrial raptor, the tawny owl (Strix aluco)

Apex predators, such as raptors, generally accumulate high concentrations of pollutants, making them excellent biomonitoring species. Tawny owls (Strix aluco) are top predators in the terrestrial environment and remain within restricted territories year-round. Consequently, each individual is expected to reflect elemental concentrations in their territory, allowing for detection of possible elemental pollution in their local environment. We examined how habitat characteristics influence the concentrations of metals and other elements in blood and feathers from adult and nestling tawny owls and evaluated these concentrations in relation to the proximity to potential pollutant sources in central Norway. Concentrations of 61 elements were analyzed using whole blood and body feathers from adult females (n = 52) and their nestlings (n = 61) during 2017-2018. Using Geographic Information System analysis, we quantified the proportion of different landscape parameters within each territory. Elemental concentrations varied significantly across habitats. Agriculture and transport pathways had the greatest impact on feather concentrations (e.g., Al, Au, Pb, Si). However, blood concentrations showed limited variation across habitats, with the presence of freshwater and transport pathways exerting only minor influence. Several elements (e.g., Ag, Al, As, Gd, Hf, K, Na, Ni, Rb, Sb, Li, V, W) showed elevated concentrations closer to potential pollution sources. Proximity to transportation pathways had the strongest overall influence on elemental concentrations in tawny owls, suggesting they represent an important local source of metal pollution. Our findings underscore the use of sedentary raptors to investigate metal pollution in the terrestrial environment and to pinpoint potential pollutant sources.