You are freezing a whole bird, and sending it to a taxidermist? It depends on how fast you ship, and how you insulate. I can send ground FedEx, and be safe. I will put the duck in an insulated cooler (the type some medicines are shipped in), and I also wrap the bird in insulation as well. I start by freezing the bird solid in two NEW freezer bags (no holes for leaks). I then wrap it in wall insulation, and tape it tight to the bird, then into the cooler that sits in a cardboard box. Tag the bird, and write the species on the outside of the box to stay legal.