Thinking my budgie is his toy

Its not entirely his fault as my budgie have no fear of anything and will scream and call to Siu Pao to chase her and then she will fly off but I am so afraid one day, there will be an accident so I am very very careful. It makes me mad coz he knows he is not supposed to chase her and is so much bigger than she is. Anyways, I have to remind budgie not to provoke Siu Pao and Siu Pao to leave her alone.