REPOSITORY > RESULTS

Abstract

We are witnessing major shifts in ecosystems due to intense anthropogenic pressures on the environment in recent decades, including rapid climate change, which is one of the strongest drivers of a global biological response. Raptors, which are at the top of the trophic web, are important indicators of ecosystem health. Tawny Owl (Strix aluco) is one of the most monitored raptor species in Europe, whose population traits may indicate various ecological processes and shifts at the ecosystem level. The goals of this dissertation were to investigate the population ecology traits of the Tawny Owl on a pan-European scale and to explore the species interactions on both inter- and intratrophic level. Our aim was to analyse the response of the Tawny Owl to fluctuations in small mammal populations, to compare it with other owls in the forest guild, and to investigate the long-term dynamics of the Tawny Owl’s competition with the Ural Owl. Our literature review on the Tawny Owl population ecology traits revealed that diet is the most extensively studied trait across Europe. Some spatial gaps in the knowledge of the ecology and biology of the species in Europe were identified, as well as gaps in certain population parameters. Based on our results, we proposed a minimal recommended scheme for monitoring population contextual data as one of the first steps towards a pan-European monitoring scheme. Our long-term monitoring data on Tawny Owl population (and other owl and prey species) from montane Dinaric forests in Central Europe enabled us to analyze its role in this ecosystem. To explore Tawny Owl’s intertrophic relationships, we used supervised machine learning approaches and addressed several modelling tasks of multi-target regression. Tawny Owl was able to successfully shift to alternative prey and sustain breeding activity even in low years of their main prey populations - the Yellow-necked Mouse (Apodemus flavicollis), which was found to have had a key role in determining predator populations. Tawny Owl, as a generalist predator and a temperate zone species, seemed to be less affected by small mammal fluctuations than its competitors, boreal zone owl species, Boreal (Aegolius funereus) and Ural Owl (Strix aluco). When further exploring Tawny Owl’s intratrophic relationship with the Ural owl, we found that due to concurrent population growth and range expansion, their competition for space and nest sites was gradually intensifying, including direct nest displacements of the smaller Tawny Owl by the larger Ural Owl. Breeding Ural Owl females were significantly larger in shared territories with Tawny Owls compared to those in unshared territories. To our knowledge, we have described the first micro-evolutionary example in top predators driven by intensified intraguild interactions enhanced by climate change. The effects of global change are complex and understanding or predicting the consequences demands excellent knowledge of the indicator species role in the ecosystem and the dynamics of its interactions in the community. We have shown that recent climate changes are also inducing rapid changes in top predator assemblages, which is just the tip of the iceberg in terms of our understanding of establishment of new ecosystem dynamics. Besides predictive models, a comprehensive and long-term population-monitoring scheme was demonstrated as an invaluable technology for following trends in ecological traits, interactions of the indicator species and for detecting ecosystem response to stress.