5. Management implications and conclusions
Overall, our findings highlight that the wintering M. squamatushas high behavioural flexibility adapted to the heterogeneous foraging environment. However, its population is decreasing continuously in recent decades and is listed as globally endangered by the IUCN (BirdLife & International, 2017). This gives an indication that the rapid anthropogenic environmental changes may be excessing or even have excessed the adaptive capacity of the species (Sih et al., 2011).M. merganser prefers to forage in clear, flowing river reaches with relatively shallow waters depth (less than 10 m), which provide diverse microhabitats, such as pools, glides, riffles, sand/gravel bars, and islands, for fish and benthic macroinvertebrates (Aadland, 1993).M. merganser is morphologically specialized in hunting moving prey in such environment (Kondratyev, 1999). The evolutionary adaptation could lose its competitive advantages as human pressures on existing habitats intensified (Lei et al., 2019) with increasing water resource developments and other activities such as sanding mining and fishing. These human pressions could dramatically change the river landscape and decrease prey abundance. For example, river regulation by damming increases water depth and reduces habitat heterogeneity (Lei et al., 2019; Swales, 2018; Zeng, Lu, et al., 2018). The endangered status of this iconic species demands researches on estimating how much habitat, of what quality, is required to sustain its population.
ACKNOWLEDGMENTS
We would like to thank The People’s Government of Shangqing Town and Forestry Bureau of Yingtan City.
Funding statement: This research was supported by supported by the Fundamental Research Funds for the Central Universities (BLX202147).
Author contributions: Author Contributions: Conceptualization, P.L., Q.Z. and G.L.; Methodology, Q.Z. and L.W.; Investigation, P.L., M.L., D.X., Y.H. and R.F.; Writing—original draft preparation, P.L. and M.L.; Writing—review and editing, Q.Z. and L.W.; Supervision, Q.Z., G.L. and C.L.; Project administration, C.L. and G.L. All authors have read and agreed to the published version of the manuscript.
Data deposits: All data for analysis is available in Dryad.