Riparian soundscape dynamics of Central European oxbow lakes: insights from year-round ecoacoustic monitoring

Abstract Oxbow lakes and their riparian habitats are dynamic but vulnerable ecosystems in intensively modified European landscapes, yet their acoustic ecology remains poorly explored. This study presents their first year-round ecoacoustic monitoring. We surveyed seven man-made oxbow lakes in the Lower Morava River Basin (Czechia) from March 2022 to February 2023 to examine seasonal and diurnal patterns of the soundscape, the effects of conservation status, and the role of surrounding land use. We compared two acoustic indices—the Acoustic Complexity Index (ACI) and the Mid-Frequency Cover (MFC)—as proxies for avian biophony, anchored by manual aural inspection of 1,380 stratified one-minute recordings. Generalized additive models revealed clear intra-annual and diurnal structuring of the soundscape, with a dominant morning peak—and a weaker secondary afternoon rise in some months—most pronounced from late winter through spring. October stood out with an increase in species richness and MFC, reflecting intensified stopover use during autumn migration. MFC tracked avian species richness more closely than ACI, while ACI remained more sensitive to local acoustic context. Protected oxbow lakes consistently exhibited higher acoustic index values and greater cumulative species richness than unprotected sites, while landscape gradients, particularly road proximity and urban cover, strongly shaped the assemblages. Year-round passive acoustic monitoring captured both natural phenological shifts and anthropogenic pressures. We recommend MFC as the more reliable biophony-tracking index for these soundscapes, with ACI as a complementary context-sensitive metric, offering a scalable tool for biodiversity assessment and restoration of small wetland systems in human-dominated landscapes.