Trophic relationship between Salix flowers, Orthosia moths and the western barbastelle

We present the results of a study which describes the relationship between the western barbastelle Barbastella barbastellus a highly specialised moth predator, and its prey—moths of the genus Orthosia, another selective animal known to converge around a dominant producer of pollen and nectar in early spring—willow trees Salix sp. In order to describe this trophic relationship, we conducted acoustic recordings at five paired sites (willow/control tree) in proximity to known barbastelle hibernation sites (Natura 2000: PLH080003 and PLH200014) beginning in mid-March 2022 after the first willow blossom sighting. Our study confirms a relationship between willow trees and barbastelles during early spring, as their activity around them was significantly higher than control sites. We also explore the activity of barbastelles over time, finding that activity levels around willows significantly decrease from the night of the first recorded bat, while the abundance of non-moth specialist bats remains consistent. Short-time importance (directly after hibernation) of willows for a moth specialist bat is probably due to other species blossom, attracting alternative prey, and in consequence—the bat. This newly described relationship should influence current conservation measures aimed at barbastelles.