Linking migratory insect and bird movements to the abundance of aerial insects

Each day and night, vast numbers of birds and insects take to the skies, engaging in migration and dispersal activities crucial for their survival. While migration has long captivated human curiosity, the dynamics of these aerial movements remain complex and in particular the interaction across taxa incompletely understood. This study explores the intricate relationship between aerial insect movements and bird migration, addressing a significant gap in the current understanding. Our study aims to bridge this gap by investigating the link between insect abundance and bird migration timing, with a closer look at aerial insectivorous species like swifts and swallows. To achieve this, we conducted a comprehensive study of insect occurrence in Pape, Latvia, during the late summer months, using vertical-looking radar (VLR) technology to monitor high-altitude insect movements. In addition to the VLR technology, ground reference data was collected using malaise traps and a Rybachy trap, providing complementary insights into insect abundance and distribution across different altitudes. The Malaise traps and the Rybachy trap showed a significant positive correlation with MTR, highlighting a strong relationship between ground and aerial insect numbers. Further a noteworthy relationship between passerine counts and insect abundance could be demonstrated. Our findings shed light on the relationship between ground-level insect activity and high-altitude migration, as well as the potential for insect occurrence to predict passerine migration patterns. By elucidating these connections, our study contributes valuable insights into the mechanisms driving migration and informs efforts to mitigate the ongoing biodiversity crisis