system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How were birds (pigeons, ravens, etc.) trained to deliver messages back in the day?
gpt
They were trained to see a place as home, by raising them there. Then they were carted off to a different place in cages. From there, they'd tie a message to the bird and let them loose. The bird goes home, message reaches wherever bird's home is. The bird then needs to get carted off again before it can be used again.