Thank you for all of the suggestions. Most of the "solutions" are far too radical for me. There will be no shootings, suits, or peace bonds.
There might be a need for me to replant some things occasionally, but peaceful coexistence will be the watchword here. These mild-mannered creatures are in no way comparable to a vicious dog. The rooster actually seems to be well trained. As soon as I tell him to go home, he walks out of my garden, clucking at his harem to follow him. One of the hens is a little addlepated, tending to run around in circles instead of getting in line with the rest of the girls, but I've shown her the way out a few times, and she'll get over her confusion, I'm sure.