Sonerud GA, Nybo JO, Fjeld PE, Knoff C. A case of bigyny in the Hawk Owl Surnia ulula: spacing of nests and allocation of male feeding effort. Ornis Fenn [Internet]. 1987Dec.31 [cited 2024Nov.22];64(4):144–148. Available from: https://ornisfennica.journal.fi/article/view/133245