Dataset Structural Equation Model - Catfolis et al.

Forests provide crucial habitats for nature and people, but also harbor organisms, such as ticks, that can act as vectors for pathogens. Consequently, understanding how forest management practices influence host-parasite-pathogen interactions is essential for promoting both forest biodiversity conservation and nature’s contributions to people. Therefore, this study investigates the complex relationships between forest structural complexity, body condition, and tick infestation probability in a common forest bird, the great tit (Parus major), across 19 forests in the Flemish Ardennes, Belgium. Using Structural Equation Modeling (SEM), we first integrated multiple phenotypic health proxies into a single overall condition index. Subsequently, we assessed how variations in forest structural complexity impact the condition of forest birds and their chances of contracting ticks. Our findings revealed that birds in a better physiological condition, primarily driven by lower levels of cellular stress (indicated by longer telomeres) are more likely to carry ticks. This may be due to ticks preferring healthier and more nutritious hosts and/or condition-linked differences in bird behavior (e.g. foraging), resulting in higher contact rates with ticks. While forest structural complexity did not significantly affect the birds' overall body condition, it was responsible for an increased tick infestation probability. Specifically, forests with higher structural complexity were associated with increased densities of questing nymphs, thereby elevating the risk of tick infestation in birds. Our study highlights the multifaceted role of forest structure in shaping host-parasite dynamics. These insights are valuable for developing forest management practices that balance the enhancement of ecological health with the mitigation of health risks posed by tick-borne diseases.