Ottvall, Richard, Lars Edenius, Johan Elmberg, Henri Engström, Martin Green, Niklas Holmqvist, Åke Lindström, Tomas Pärt, and Martin Tjernberg. “Population Trends for Swedish Breeding Birds”. Ornis Svecica 19, no. 3 (July 1, 2009): 117–192. Accessed May 17, 2022. https://journals.lub.lu.se/os/article/view/22652.