Literal translation
he is the bird on the branch that flies off at the slightest noise
Meaning
he's ready to flee at the slightest noise
Explanation
This saying describes someone permanently on edge, unable to settle anywhere for long, ready to bolt at the first alarm. The literal image is that of a bird perched on a branch, never truly at rest, ears pricked for the slightest snap of a twig or rustle of leaves, and which flies off the instant it hears one. The comparison works because a bird, unlike a creature that can retreat into a burrow, has no defence but instant flight, so it embodies nervous vigilance. The phrase is used for a fearful, wary temperament, often shaped by some past experience that has made flight an automatic response. The register is familiar and vivid, the kind of comparison used when describing someone's character at the market or around the family table. The relative clause placing the trigger, the noise, before the consequence, the flight, underlines the disproportion between a minimal cause and an immediate, total reaction.