Repellers and bird control

Technical specifications
All these remedies against birds have one characteristic in common, do not cause them any harm and are not polluting.
The spray makes the bird run away with a strong smell that disgusts the bird.
On the other hand, ultrasound is small infrared speakers to detect bird movements and emit voices of eagles, hawks.
One more option is the figures of owls and the like, with reflective eyes and rotating head.