What is the origin of the idiom "the bird has flown" and when to use it?

The idiom "the bird has flown" originated from the practice of falconry, where a trained bird of prey, like a falcon, was used to hunt. If the prey managed to escape or fly away before the falcon could catch it, the falconer would say "the bird has flown." This phrase then evolved figuratively to describe situations where a person being sought after has eluded capture or disappeared, conveying the notion that target has escaped.