That is a wing band ID tag. The advantage to a wing band over leg bands is that the bird never outgrows it. It is a piercing and will stay there for the life of the bird. It will eventually be hidden by feathers but still there and readable if you catch the bird and spread the feathers out.
This is the first time I’ve ever used them so far I do like them. I was a bit nervous to do it the first time but the birds didn’t seem bothered at all. No blood and no sign that the even felt it. They were just a bit upset that I was holding them still during the process.
Attached is a close up of #006. The black spot on his head is the reminder of the sharpie I marked it with for id the first week before I tagged him
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