Sorry, forgot the mold issue,
One might try and keep the plants limited and as far away from each other as possible so the proper air and sun light can effect each plant, when there are to many plants and close together moisture is trapped causing mold to develope.
Here's a site that might be able to help you.
Gray Mold
I admire your intentions to create a natural enviroment for your birds.
Good Luck
BW