Thanks for the help, y'all!
I had already been looking at the poultry2.tripod site, so it was nice to have it mentioned. I just ordered from them, so we shall see.
Where do you all buy your adult bird shipping boxes? I am getting ready to list a bunch of silkies up for auction and want to go ahead and have the boxes before I do so. What is my best source for post office approved adult shippers?