Drivers of the spatiotemporal dynamics of the local breeding population of the endangered Scaly-sided Mergansers Mergus squamatus

Abstract

Scaly-sided Merganser is an endangered species confined to eastern Asia, primarily breeding in southeast Russia and northeast China. Its breeding range is quite large, with limited information on population dynamics. The Kievka River catchment in far east Russia is one of the most densely populated breeding grounds, providing the only extensive, long-term monitoring on breeding Scaly-sided Merganser. This study assessed the current status of Scaly-sided Merganser and investigated the environmental factors influencing the population. From 2014–2021, the population size at each river reach fluctuated with no directional trends, while the density of Scaly-sided Merganser increased. The result suggested a higher concentration of breeding Scaly-sided Merganser in Kievka River catchment in recent years, particularly preferring downstream area. The species also demonstrated an affinity to less riparian vegetation and higher flow rates. Notably, river flow rate emerges as a potential key issue for designing environmental flows of the breeding habitat for Scaly-sided Merganser, presenting a challenge for researchers and managers.

Keywords

• Scaly-sided Mergansers
• River
• Flow rate
• Breeding
• EVI
• Population dynamics