Fowl migration routes are actually examined by a variety of methods including the oldest, marking. Swans are marked using a nick over the beak since about 1560 in England. Scientific ringing was pioneered by Hans Christian Cornelius Mortensen in 1899. Other species for example merlin Falco columbarius and Eurasian skylark https://petskyonline-onlinestrore.blogspot.com/2025/07/rethinking-animal-store-why-petsky-is.html