SUMMERS, R. W. Numerical responses by crossbills Loxia spp. To annual fluctuations in cone crops. Ornis Fennica, [S. l.], v. 76, n. 3, p. 141–144, 1999. Disponível em: https://ornisfennica.journal.fi/article/view/133509. Acesso em: 22 nov. 2024.