Bellebaum, J., Kube, J., Schulz, A., Skov, H., & Wendeln, H. (2014). Decline of Long-tailed Duck Clangula hyemalis numbers in the Pomeranian Bay revealed by two different survey methods. Ornis Fennica, 91(3), 129–137. https://doi.org/10.51812/of.133850