FERNS, P N; REED, J P; GREGG, E D; O’HARA, C; LANG, A; SINKOWSKI, G R. Bill knob size and reproductive effort in Common Shelducks Tadorna tadorna. Wildfowl, [S. l.], p. 47–58, 2013. Disponível em: https://tidsskrift.dk/Wildfowl/article/view/153938. Acesso em: 13 feb. 2026.