I remember one late night I was at a large USPS center for work, and there were a bunch of packages sitting nearby. I was talking to the USPS official about the work that needed to be done, and suddenly... one of the packages moved! I nearly jumped out of my skin and told him that the package moved! He was very calm, and said "yep, those are geese". And then proceeded to tell me all the different types of animals (and bees) they routinely ship.