Gowans, Billie, Gregory J Robertson, and Fred Cooke. “Behaviour and Chronology of Pair Formation by Harlequin Ducks Histrionicus Histrionicus”. Wildfowl (January 1, 1997): 135–146. Accessed December 17, 2025. https://tidsskrift.dk/Wildfowl/article/view/154109.