If you could place the cage legs or the bottom of the cage in water, that would keep them out on the ground. Then ensure there’s no contact with higher up things so they can’t access that way either

Are the ants stealing your bird’s seed? I personally have seen them stealing carrot seeds from under the soil in the garden after watching diligently. If you are giving them fresh fruit from your garden, the ants may already be in them. Imagine my utter disgust when I dicovered tiny little pin size holes in fresh apricots on our tree. They weren’t even ripe. Part of their skins were still light green. Whne we picked them we instantly had ants running on our hands. They could be on grass you are giving them or other green leaves you are giving them.

wow never heard of that before, maybe make sure any fruit etc is removed as soon as finished eating, pour ant sand around outside of aviary, but yeh never heard of that before if ant problem is that bad that they are eating your baby bird you might need to get a professional in.

Maybe get some advice from a bird breeding specialist?

Have the aviary free from branches and leaves from trees and shrubs. Find the green ant next and destroy it. The nests will be in nearby vegetation. You can follow the trail of ants back to their nest. Diatomaceous Earth can be sprinkled around the floor of the aviary. It will not hurt the birds, but will kill ants and all other insects.