Habitat Selection and Negative Effect of River Regulation on the Abundance of the Common Sandpiper (<scp><i>Actitis hypoleucos</i></scp>), a Riparian Shorebird

ABSTRACT Rivers and other freshwater ecosystems have been severely changed by humans. This resulted in a distinct decline in the abundance of many aquatic organisms, as well as those living in water‐dependent habitats. Our work aimed to study the habitat selection of breeding common sandpipers ( Actitis hypoleucos ) and the impact of river regulation on the occurrence of this species. Data were collected on a 100‐km stretch of the Vistula River, a semi‐natural, lowland and large European river. The distribution of birds was determined based on two censuses, while environmental variables were collected based on Sentinel‐2 satellite imagery classification, digital elevation model (DEM), digital surface model (DSM) and official data of river regulations. The length of the shoreline of either the river or vegetated islands had a positive effect on the number of breeding territories of the common sandpiper. This indicates the importance of the presence of a natural riverbed with a complex shoreline. Moreover, sandpipers preferred islands over the river shores as nesting habitat. River regulations, such as groynes and riprap, had a negative impact on the abundance of breeding common sandpipers even though the river regulation was not intensive. The negative effect has been persisting for many years after the regulation was implemented, despite the degradation of regulatory structures over this period.