Fowl migration routes have already been analyzed by many different techniques including the oldest, marking. Swans are marked using a nick about the beak given that about 1560 in England. Scientific ringing was pioneered by Hans Christian Cornelius Mortensen in 1899. A lot of massive birds (like eagles and vultures) https://letusbookmark.com/story22229951/5-simple-statements-about-pet-shop-dubai-explained