Solheim, Roar. “Moult Pattern of Primaries and Secondaries During First and Second Flight Feather Molt in Great Grey Owls Strix Nebulosa”. Ornis Svecica 21, no. 1 (January 1, 2011): 11–19. Accessed May 1, 2024. https://journals.lub.lu.se/os/article/view/22610.