Here's why:
* Movement can be varied: Robins hop, walk, fly, and even flutter their wings.
* Movement is often described by action: We might say a robin is hopping, fluttering, or flying.
If you're looking for a specific term, consider what the robin is doing:
* Hopping: A quick, light jump on the ground.
* Walking: A slow, deliberate movement with alternating feet.
* Flying: Movement through the air using its wings.
Let me know if you have a more specific type of movement in mind, and I'll try to help!