Unless it's some sort of flood protection or something, I've no idea as that Area as I understand wasn't to be done for this part of the development of islands. I imagine someone will know and can tell you.
@Ag999 I've no clue sorry, It may be behind the monsoon forest area , obviously this isn't he view of the hole sight so it will be there besides aviaries are often built later, I think as hey are much faster, there is a bit less foundation work ec, in my opinion, again I'm not sure