Owl-mediated diploendozoochorous seed dispersal increases dispersal distance and supports seedling establishment

Seed dispersal is an essential process contributing to the maintenance of plant populations. Zoochory is a widespread way of plant dispersal in every terrestrial ecosystem that can ensure the long-distance dispersal of seeds. Secondary seed dispersal (SSD) by far-ranging raptors is a special type of zoochory, which might have a role in colonizing new habitats. We used the barn owl (Tyto alba) as model species to test the effectivity and seasonality of SSD in open semi-natural landscapes. We collected 582 pellets from six sites in East-Hungary throughout one year. We identified prey items in the pellets and determined the viable seed content of the pellets by germination experiments. We found that herbivorous Microtus arvalis L. was the most abundant prey item through which most of the seeds spread. Owls dispersed the seeds of generalist and disturbancetolerant plants, indicating the habitat type where small mammals occur abundantly. In another experiment we tested the effect of the pellet material on the seedling survival and found that prey remains enhanced establishment of seedlings. Our study suggests that SSD by barn owl is occasional but important event in long-distance seed dispersal. Since the studied owl species uses several habitat types and has larger mobility than the rodents, the revealed dispersal mechanism can considerably increase seed dispersal distance and seed exchange between habitat types.

Automated summary

Seed dispersal is crucial for the survival of plant populations, and zoochory is a widely observed method that enables long-distance dispersal through animals. Secondary seed dispersal by far-ranging raptors, such as barn owls, plays a role in colonizing new habitats. In this study, we found that barn owls primarily dispersed seeds through herbivorous Microtus arvalis, indicating the importance of habitats with abundant small mammals. Furthermore, the remains of prey enhanced seedling establishment, suggesting the potential of barn owl-mediated seed dispersal to increase dispersal distance and seed exchange between habitat types.