system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do small birds tend to hop while bigger ones walk?
gpt
Most birds that hop are passerine or perching birds. They have a special anatomy in the legs that makes the toes clench when the leg is relaxed, allowing them to sleep while hanging on to branches or telephone wires, or whatever. Birds that don't have this anatomical adaptation walk or strut more normally.