May, Roel, Jiska van Dijk, and Bård Gunnar Stokke. “Which Characteristics Are Important for Species Identification of Birds in Flight? Results from a Survey of Norwegian Birdwatchers”. Ornis Norvegica 48 (November 10, 2025): 12–18. Accessed December 5, 2025. https://boap.uib.no/index.php/ornis/article/view/4196.