Pointless albatross
A pointless albatross is a large sea bird that doesn't think twice about flying for thousands of miles without stop for just a can of anchovies, and the removal of an uncomfortable thing on the bird's leg. It seems to the bird that it's worth a flight of several thousand miles and, after only a short rest, the same length of flight back home. For this reason, the Agatean Empire uses pointless albatrosses as messenger birds (as other people might use pigeons), often to Ankh-Morpork.
The albatross's pointless missions can be found in: The Colour of Magic, Interesting Times, Small Gods and The Last Hero.