The best way to send a bird, is take the bird, and freeze him solid. Put it in two freezer bags to prevent leakage during transport. You must tag the bird with your name, license number, date of kill, and where it was killed. On the outside of the box, you must label it "Red-breasted merganser". After you freeze the bird, and are ready to ship, wrap the bird in as much insulating stuff as possible. I like to use insulation like you would use for a wall. Make sure you block out all the air inside the box. So if there is a corner that needs filling, stuff some balled up newspaper and stuff it. I like to freeze the entire wrapped box, and take it to the delivery place (FedEX, USPS, or UPS) before they are going to ship. No need to have it sit in a warm building. If the bird is insulated properly,you can get by sending it ground. I used to pay the price to have it sent overnite or priority, but have learned and taught others how to insulate properly. It saves a ton of money sending it ground, and if done right, the package will still be cold, and many times still frozen. I sent a black duck to a buddy in Texas, and a goldeneye to another buddy in Texas, on the same day. I sent them ground in those coolers that medicine arrives in, wrapped in insulation, and sent them ground. It took four days to get there (including the day I brought it to FedEx), and both arrived still frozen. Those same packages would have been over fifty bucks next day delivery, and instead they were less than 14. I also set up a FedEx account, and if you print your own label, you can save the recipient even more money. You cannot charge for handling nor the stuff to ship it, nor the gas to take it to the delivery store. If the package costs $14.83, you charge 14.83. It is easiest to have the recipient set up a FedEx account, and then there is zero money transacted due to the recipient paying for the delivery via his account number.
By the way Slack Tide, very nice of you to offer those birds. As you know, many people take for granted the birds they shoot, when in fact, another guy in another place will never lay eyes on one. Like the guys in Texas who got a black duck and a goldeneye. Those are not birds they will ordinarily ever see, and they were pleased as punch to get them.