If you've ever seen a big clump of bees clinging to a tree branch, it was probably a bee swarm. They're typically seen in spring and summer, when honey bees head off in search of a new home.
This podcast episode discusses bee swarms, how beekeepers can stop their bees leaving, and what non-beekeepers should do if they spot one.
Check out the full article here: https://beeprofessor.com/what-is-honey-bee-swarming/