SONERUD, G. A.; NYBO, J. O.; FJELD, P. E.; KNOFF, C. A case of bigyny in the Hawk Owl Surnia ulula: spacing of nests and allocation of male feeding effort. Ornis Fennica, [S. l.], v. 64, n. 4, p. 144–148, 1987. Disponível em: https://ornisfennica.journal.fi/article/view/133245. Acesso em: 21 may. 2024.