Densities of the willow warbler, Phylloscopus trochilus (L), doubled in a year

Siivonen, L. (1950). Densities of the willow warbler, Phylloscopus trochilus (L), doubled in a year. Ornis Fennica, 27(3), 68–72. Hämtad från https://ornisfennica.journal.fi/article/view/132529