So these were on the legs of the Cayuga ducklings I just bought home, ostensibly to identify them as girls. They looked flexible, so I didn’t get them off immediately, I finally caught up with my wife last night and we tried to take them off, they were so stiff and tight I had to cut one off, the other required 2 pairs of needle nose pliers because I couldn’t get hold with my fingers. They had an indent on their legs where the band was, but seem to be fine now. Are these an actual band for the purpose or is it something else? I am worried about the other ducks that we didn’t take.