perch-site selection in shrikes: effects of human disturbance in Poland and Loas

Background. Anthropogenic pressure, including hunting and habitat modification, is a major driver of behavioral variation in birds, particularly in regions differing in conservation regimes and human disturbance. Flight initiation distance (FID) is a widely used metric of antipredator behavior that reflects both immediate risk perception and longer-term behavioral adjustments to human activity. This study compares habitat selection and escape responses of two closely related species, the Red-backed Shrike (Lanius collurio) and the Brown Shrike (Lanius cristatus), occurring in regions with contrasting levels of human pressure: Central Europe (Poland) and Southeast Asia (Laos). We tested whether the two species differ in their use of perching sites relative to roads and built-up areas, and whether FID is shaped by proximity to human infrastructure and species identity.
Methods. Field data were collected in spring 2024 in agricultural and peri-urban landscapes in Poland and Laos. A total of 171 perching sites were recorded (102 Red-backed Shrikes and 69 Brown Shrikes). For each observation, flight initiation distance (FID), starting distance (SD), perch height, and distances to the nearest dirt road, asphalt road, and built-up area were measured. Determinants of FID were examined using linear models with log-transformed response variables. Model selection was based on an information-theoretic approach using AIC, and only models with ΔAIC ≤ 2 were retained for inference.
Results. Perch-site selection differed significantly between the two species. Brown Shrikes occurred at greater distances from built-up areas. FID was significantly greater in Brown Shrikes than in Red-backed Shrikes. Distance to the nearest built-up area had a negative impact, while the SD had positive impact on FID. These results indicate that shrikes inhabiting regions with higher hunting pressure exhibit stronger avoidance behavior and altered spatial responses to human infrastructure, highlighting the role of regional anthropogenic context in shaping antipredator behavior.