Geographical and Habitat Factors Affecting Migratory Waterbirds Along Rivers in the Palearctic

Abstract

1. Rivers are important habitats for many waterbird species, offering crucial resources such as feeding and resting areas during migration. The migratory patterns of these birds are influenced by a variety of factors, including geographical location, habitat availability and environmental conditions. Despite the huge ecological importance of rivers, there are few studies on how riverine environments support migratory bird populations across a broad geographical scale.
2. This study aims to identify the key determinants of migratory bird distribution, species richness and abundance within river systems.
3. The study was conducted during the autumn migration of birds in temperate zones of Europe and Asia. Through a combination of ecological assessments and statistical analyses, we identified the primary factors influencing migratory bird distribution, species richness and abundance.
4. During migration along 14 large, unregulated rivers, we recorded 63,383 individual birds, representing 112 species. Analysis revealed significant associations between species richness and bird abundance and geographical proximity, with neighbouring rivers displaying greater similarity in species composition and density. The presence of sand banks and islands emerged as critical factors influencing species richness and bird abundance, while forested river segments negatively impacted species richness compared to open landscapes like agricultural areas. River width had no significant effect on avian assemblages.
5. This study highlights the crucial role of habitat structures, particularly sand banks and islands, in supporting diverse waterbird populations. Our findings highlight the vulnerability of these habitats to anthropogenic alterations, which may adversely affect migratory waterbird numbers.