thanks hitch, i posted it over on the refuge and a guy from out west that does some banding gave me some interesting info on it.said that they are used on little ones primarily cavity nesting ducks and they have clay that fills up the hole in the band except for a small portion.this allows them to be placed on young ones and the clay desolves slowly as the bird grows.said that they are starting to use this technique a good bit now.neat stuff, i learn something new about these critters, that so consume my life, every day...