I am trying to do some research to find out why a bird sold as a pet would even have a band on its leg. All I have found is some info about putting the age and breeder info on this band. The cockatiel we are getting does not have a band on its leg. Should all birds have some type of band on their legs? Is there different laws in different states? I was curious particularly because of the last comment about keeping the pieces of the band incase there were problems in the future. I don't think I would want a band put on our little cockatiel's leg.
Leg bands are used for identification purposes. With the normal, slip on bands, chicks are banded when still in the nest. It will contain an identification number, breeder code (sometimes traceable), and hatch date. Some states require that certain types of birds be banded. If a banded bird escapes and is recovered, then knowing the identification number will help them know that the bird is yours.
Many breeders will band their birds with traceable bands that way if someone wants information on the genetics or family line it can be found out with some searching. People who show their birds may also have to have closed banded birds, but I'm not sure about that. If someone decides at a later date to breed their bird, they can use breeder information found on bands to help them find an unrelated bird.
Bands, when done correctly rarely bother the bird, kind of like us wearing a loose bracelet. As I said before, my oldest tiel has been wearing his for 20 years with no problems.
Open or split bands were used on imported birds. The information on those would have contained an ID number, place of quarantine, and I believe the year they were imported. Many parrot type birds are able to open these and they can cause problems, but I don't know about the legality of taking them off.
The reason I say to take photos and save the pieces is just in case there are any laws passed about having pet birds banded in their state. I highly doubt that there will ever be any issues with cockatiels, but you never know. This is one of those cover your butt situations.
Also, if they file a report with animal control about the unhealthful (abusive) situation at the store, then photos and a vet's report will be helpful. By banding this paticular bird with an open band, they could be trying to pass off birds as older than they are or fake breeder info. I don't see any profit in this, so I don't understand the reason for this paticular band.