Swennen, C., Duiven, P. and Wintermans, G. J. M. (1989) “Abnormal plumage in possibly senile female Eiders Somateria mollissima”, Wildfowl, pp. 127–130. Available at: https://tidsskrift.dk/Wildfowl/article/view/154006 (Accessed: 17 December 2025).