The Lucky Ducky Letter Exchange

You know, someone once tried to use a goose to duplicate the success of the Exchange. It... did not go as planned.

— Jasper Cameron, Leader of the Bronze Ravens

The history of the Lucky Ducky Letter Exchange is somewhat shrouded in legend, but I will try to dispel some of that here and stick to the facts where I can.
Sometime in the past, before the Necromancer Wars but after the fall of The Storm Giant Empire someone at one end of the Dragon's Spine Mountains decided that they were going to follow the ducks on their annual migration. Depending on where you hear this story you will hear a number of different reasons for this ridiculous quest. A hunter challenged a rival that he couldn't track the same duck for a whole year or an impossible challenge was given to a prospective suitor to prove their worthiness, something silly like that. A duck was marked with a ribbon, or a magical token, or chosen because of a unique feather pattern, which is most likely, and then the person set out to complete this impossible task.
Along the way the person learned some magic, or met a wise hermit, or earned the favor of a god, you get the picture. They were able to keep up with the duck, no small miracle when traversing a mountain range. Each night they would make camp near where the ducks had landed, and the next day they would set out again, always keeping the "V" just in sight. No storm darkened the sky (or perhaps one did and they heroically pushed through it) and eventually they came to where the ducks spent their winter. There were (surprisingly) people there, as well as near many various lakes along the way. On the way back the ducks stopped in the exact same lakes.
Sadly, the designated duck was shot by a hunter, or killed by an eagle, or a fox. No one believed the person had succeeded when they returned with the ducks the next year. So they said they would do it again, and send a letter with a token back by duck, before returning this time after 2 years. This time they succeeded in their task.
Now seasonal communications are sent up and down the Dragon's Spine Mountains using the Lucky Ducky Letter Exchange. to address a letter one need simply know the color code for the town it is going to. All towns that participate have feeding stations set up for the ducks, to attract them to town and allow for the retrieval and sending of letters. When the flock lands, take any letters bearing your town's designated color, attach any that you want to send bearing the receiving town's designated color, and let the ducks go on their way.
Usually more than one copy of a letter is sent on separate ducks. After all, while the ducks are now friendly after thousands of years of this practice, they are not tame, and accidents do happen in the wilds between towns. Still, the residents of these mountain lake towns are incredibly well informed of the goings on in the wider world, and its all thanks to the to the Luck Ducky Letter Exchange.