I have two budgies. I've had them for three weeks. Whenever I approach their cage, they get a tense. When I put my hand in the cage to change their water/food, they scuttle away and when I try to see if they would perch on my hand or hand-feed them some food, they fly around the cage trying to get away from my hand. How do I get my budgies to not be afraid and warm up to me?