Woodpeckers as Indicators of Avian Richness in Non-forest Tree Stands: A Case Study of Rural Parks in the Agricultural Landscape of SE Poland

Assessing the conservation value of biodiversity refuges requires effective diagnostic tools, among which indicator species may play an important role. This study presents the first evaluation of woodpeckers Picinae as indicators of bird species richness in non-forest tree stands. The evaluation was carried out in spring 2018 in 71 rural parks located within an agricultural landscape in southeastern Poland (2140 km²). We assumed that a higher number of woodpecker species would signal parks with richer avian communities, particularly cavity-nesters and forest-associated species. The results confirmed the high diagnostic value of woodpeckers: parks occupied by woodpeckers supported richer bird assemblages and a greater proportion of tree-dependent species. In contrast, parks without woodpeckers were dominated by synanthropic and eurytopic species typical of open or heavily modified habitats. The Great spotted woodpecker showed the strongest indicator value, being closely associated with cavity-nesters and species requiring mature tree stands. We conclude that woodpeckers could serve as effective indicators of biodiversity refugia in agricultural landscapes and can support monitoring and conservation planning for non-forest tree habitats.