Invasive raccoons threaten bird populations in Ujście Warty National Park

Researchers from the University of Warsaw have identified 14 breeding sites for invasive North American raccoons within the Ujście Warty National Park in Poland. The study, published in the Journal of Vertebrate Biology, reveals that these predators are occupying tree hollows and wooden nesting boxes intended for ducks, posing a significant threat to protected bird species.

Monitoring via camera traps has shown low breeding success for birds such as goosanders and mute swans, as birds constitute approximately 25 percent of the raccoons' diet. The study notes that raccoon populations in Poland appear to be thriving, with an average litter size of over four young, which exceeds the average of three observed in similar studies in Germany.

While existing protections like spikes and collars deter native predators such as martens, they have proven ineffective against raccoons. Researchers suggest that the most effective defense is the installation of slippery plexiglass trunk covers at least one meter in height to prevent the climbing animals from reaching nesting sites.