On the occurrence of the Grasshopper Warbler (Locustella naevia) and River Warbler (L. fluviatilis) in Finland related to the bird watching activity. Ornis Fenn [Internet]. 1969 Sep. 30 [cited 2025 Nov. 6];46(3):113–125. Available from: https://ornisfennica.journal.fi/article/view/132768