Intensification of intraguild interactions between top predators in a climate change impacted environment: a new potential evolutionary pathway

Adaptations of coexisting species to climate‐driven environmental changes might not necessarily lead to extinctions, but rather to trait variations that generate new competitive hierarchies in ecosystems. Top predators have a pivotal role in ecosystems, but long‐term effects in changing environments have not been sufficiently explored. We used long‐term data on the territory (n = 65 survey points) and breeding (n = 69 nest‐boxes) dynamics of two coexisting, ecologically similar and closely related forest raptors, the warm‐tolerant tawny owl Strix aluco and the cold‐tolerant Ural owl S. uralensis , in temperate central‐European montane forest that has experienced significant climate change (> 1°C mean temperature increase) but not habitat change in the period of 20 years (1998–2021). We have found concurrent increase in the number of territories in tawny (+2.6% annually) as well as in Ural owl (+5.2% annually). The number of overlapping territories increased by 11.0% annually. After year 2012 we observed a gradual intensification of competition for space and nest sites, including direct nest displacement of the smaller tawny owl by the larger Ural owl (16.5% of nest‐boxes). Competition did not affect breeding success but apparently affected breeding Ural owl females being significantly larger (measured as head length) in shared territories with tawny owls compared to those in unshared territories (mean difference of 1.3%). From an evolutionary‐ecological perspective, this size disparity could bolster the Ural owl's dominance over the tawny owl. However, it could also pose long‐term risks for the Ural owl, as the advantages of larger size come with increased energy demands and reduced hunting agility. This study highlights that, beyond theoretical model predictions, robust long‐term monitoring data are urgently needed to capture the actual changes taking place due to the effects of global warming and to reveal the hidden and trait‐based adaptations of coexisting species and unforeseen drivers of extinction.