Annual bird diversity in a riparian forest–agricultural landscape mosaic in the Raba River valley, southern Poland

Riparian forests and adjacent low-intensity farmland can support very rich bird communities, including species associated with river valleys and declining agricultural landscapes. These habitats are also important for wintering birds and migration, but are increasingly threatened by river regulation, urban expansion and agricultural intensification.

This study assessed year-round bird diversity in a riparian forest–farmland mosaic, with particular emphasis on breeding species. From spring 2020 to spring 2021, weekly bird surveys were conducted along a 4-km section of the Raba River valley bordering western Bochnia, southern Poland. The area included riparian forest and an adjacent mosaic of meadows and extensively managed fields. During each survey, bird species were identified and the number of individuals was estimated. In the breeding season, breeding pairs were additionally counted and breeding evidence was assigned to standard categories.

In total, 100 bird species were recorded, including 70 classified as breeding or probably breeding. The breeding assemblage included Annex I Birds Directive species: Corn Crake Crex crex, Black Woodpecker Dryocopus martius, Common Kingfisher Alcedo atthis, Red-backed Shrike Lanius collurio and Barred Warbler Curruca nisoria. European Turtle Dove Streptopelia turtur, a rare and declining farmland species, was also recorded as breeding. Particularly high breeding densities were noted for Red-backed Shrike, River Warbler Locustella fluviatilis and European Stonechat Saxicola rubicola. Although wintering and migrating birds were recorded, the area appeared most important during the breeding season.

The results show that a small river-valley section combining riparian forest and extensively used farmland can sustain high bird diversity and important breeding populations of conservation-relevant species. A repeat survey initiated five years later suggests declines in some farmland birds and the apparent disappearance of Corn Crake and Turtle Dove, coinciding with ongoing development of meadows. These findings highlight the need to protect riparian–farmland mosaics as biodiversity refugia in urbanizing landscapes.