WATSON, A.; MARQUISS, M.; SUMMERS, R. Abundance of crossbills, Siskins and cone-crops. Ornis Fennica, [S. l.], v. 86, n. 1, p. 38–40, 2009. Disponível em: https://ornisfennica.journal.fi/article/view/133719. Acesso em: 21 may. 2024.