@Westcoastperson There are no free flight birds in the aviary. Barriers can be in place for reasons other than containing zoo animals; it could be to keep wild animals out, for example. I don't know the reason this specific enclosure was designed like this.
@Coelacanth18 yeah I have heard of netting being put over to avoid animals like raccoons or raptors but I’ve never heard of one necessary for African Penguins.