[1]
O. Hildén, “Diurnal rhythm of colony attendance and optimal census time for the Black Guillemot Cepphus grylle in the Baltic sea”, Ornis Fenn, vol. 71, no. 2, pp. 61–67, Jul. 1994, Accessed: Nov. 28, 2025. [Online]. Available: https://ornisfennica.journal.fi/article/view/133394