I understand that the adult bird boxes like horizon have filters in them and are approved for shipping live birds, but the boxes used for chicks is really no different than a regular box with holes in it. So I asked the woman at the post office today if I had to use the chick boxes I had been and she said no that it did not matter and I could make chick shipping boxes out of the priority mail ones the give away if I wanted. Is this true? has anyone done this? I figured I could reinforse the box and add bedding and holes like the ones I got from the hatcheries and mark it the same. I would only want to do this with chicks and quail seeing as they are small and would use the regular horizon boxes for juviniles and adults.