I have a small-medium yard in a small city, fenced in. It's fenced in well enough to keep the chickens in, but there are lots of trees and such, and no doubt if something like a raccoon or coyote really wanted in, it could likely find a way. My question is.... can I let my chickens free range, with access to their tractor, while I'm at work? Or are they too vulnerable? I could just let them out when I'm home? Are predators a problem during the day, or mostly just in the evenings and night-time? Thanks!