strategies of Mute Swans
Description
An important factor influencing nesting strategies in birds is interspecies interaction, often shaped by competitive behaviours. The expansion of a more territorial species can intensify negative interactions, leading to increased competition with native species. This study investigates how the presence of Whooper Swans Cygnus cygnus affects the nesting strategies of Mute Swans Cygnus olor, with a particular focus on changes in nest site selection. Fieldwork was conducted at two study sites in central and southern Poland, encompassing both single-species and mixed-species nesting environments. We measured a range of spatial variables, including proximity to open water, vegetation cover, and spatial relationships between nests of competing swan species. A novel method was developed to quantify nest concealment and isolation in complex habitats, integrating multiple habitat and spatial metrics into three indices. Mixed linear regression models revealed that Mute Swans adapt their nesting strategies in the presence of Whooper Swans by selecting more concealed and isolated locations. This behaviour is interpreted as a trade-off between optimal nesting conditions and the need for protection from aggressive competitors.