Decaying Logs Shape the Distribution of Bird-Mediated Seed Rain in a Temperate Deciduous Forest

Birds contribute to seed dispersal through endozoochory, often creating spatially aggregated patterns of seed deposition around perching sites. While this process has been extensively studied in open habitats, the role of deadwood in structuring bird-mediated seed rain within forest ecosystems remains poorly understood. This study investigated whether decaying logs function as important perching sites which influence the distribution of bird droppings and associated seed rain in a temperate deciduous forest. Bird droppings were collected during three seasons in 2021-2023 in an oak-hornbeam forest, using seed traps placed either beneath decaying logs or at randomly selected forest-floor locations. A total of 524 droppings were recorded. The abundance of droppings was significantly higher beneath logs than in random plots throughout the study period, with 73.7% of all droppings found in log-associated plots. This created a strongly aggregated pattern of seed deposition, as 80.6% of all recovered seeds occurred beneath logs. Overall seed dispersal by birds was low. Only 4.6% of droppings contained seeds, and mean seed rain reached 0.39 seeds × m^-2 × season^-1. These findings suggest that although bird-mediated seed input is limited, its distribution is strongly shaped by deadwood availability. Decaying logs therefore represent an overlooked structural component linking birds and fleshy-fruited plants.