Will cats be a threat? Since their nest is so high, there would be no danger until the little birds leave the nest. Do they feed the babies on the ground? I had a terrible time last year with Spanky and the wrens.

No, they bring insects to the babies and there is a little rail around each floor. I just saw the little heads sticking out the door when they heard the parents coming with feed. They looked almost grown before they flew away. My cats never even paid them attention. They are fast, flitting and swooping type birds.