Pakkala, Timo, Juha Tiainen, Heikki Pakkala, Markus Piha, and Jari Kouki. 2020. “Nest Tree Characteristics of Grey-Headed Woodpeckers (Picus Canus) in Boreal Forests”. Ornis Fennica 97 (3):89–100. https://doi.org/10.51812/of.133969.