You seem to be having a few problems... Im glad I live in the UK... its cool most of the time, so my birds stay in side... I'd luv to have an aviary but its not possible where I live...

why is it not possible?

I wish I would have a normal aviary, not a porch that is used as aviary (all the problems originate from this fact). But, I really love to see how much more energy my birds are having after spending couple of hours out each morning.
My house is really dark inside, unfortunately. They were in a sleepy mood a lot while inside.

Jan, I think it's very amazing that my birds now have the opportunity to feel a little bit as a part of nature where they should belong... Problems are fixable.
Yes, it's damn hot this days and I hate it! but I hate air-conditioning even more! I wish I would live in a normal climate without extreme. It's 36C today, and has been recently. Last weekend it was even hotter.
My poor rabbits really suffer outdoors (from the heat), so I am working on bringing them indoors. But I feel sorry for rabbits whose owners NEVER take them out, having them as entirely indoor pets.
I just love nature and outdoors.... sun, wind and nature noises.

One thing you could do to keep the birds away from the mortar is to make some wire panels similar to the ones that you used to close off the open space, and put them in front of the bricks. That would reduce their chewing options!

I just saw that I have a real ant infestation on the screen from outside. Interesting, no ants can be seen on the inner part but I still need to deter them. I wonder how tiels would like tea tree oil smell ? Is it safe to use around birds?

you should realize that bricks are everywhere! Its easier to build a brand new separate aviary I think

I've heard of problems with tea tree oil so I'd avoid using it close to them. Can you figure out where the ants are coming from? If their ant hill is far enough away from the porch, you can treat the problem there at a safe distance from the birds.

ok the situation is pretty bad here, birds are not let out today as I am trying to fix ant problem. Interesting, with screens assembled, you would occasionally see one or two ants if you are standing on the porch inside of the bird area. But if you step outside... mama mia...I am posting a picture. They travel on the vertical bricks under the very top step coming from the right side (of the pic)..then they travel up on black metal bars, to where black metal bars are attached to the yellow wooden part of the roof. yesterday they were traveling back and forth carrying white particles - I couldn't identify what it was but it was obviously something valuable for them. Today I discovered that there is a gap between yellow wood and black metal (on the top) - it's a very thin slit, maybe 10 inches long but rather deep. I inserted my knife into the slit and immediately regretted as tons of ants came out (eventually there is a hollow in the yellow wood where they attached metal bars). We need to seal the gap with something non toxic. My hubby suggests Caulk. Is it toxic? Birds will never have access to the seal itself (by the way the screens are) but they could be a few inches away.
As for the broad solution of the problem... I don't know yet. Right next to the porch (to the right on the picture) there is a fence where rabbits have access to (and ants do travel on the fence!)... will need to work on that later... I would prefer something non toxic though.
PS I heard that it's not advisable to massively kill ants - they are important part of environment

It seems likely that the ants are living inside the slit, since I wouldn't expect there to be anything inside there that they can eat. The stuff they're carrying might be food supplies or even eggs if they're moving in from somewhere else.

Ants are an important part of the environment and it wouldn't be good to go on a massive campaign to exterminate them all, but most people don't think there's anything wrong with getting rid of a single colony that's in an inappropriate place. You can be sure that there are lots more ants in the general area so you won't be making a serious dent in their population.

Caulk would be OK as long as the birds don't have the opportunity to try and eat it. It can be dangerous when swallowed but otherwise it isn't a problem. Caulk doesn't usually have much of a smell even when it's wet if I remember right, and once it's dry there shouldn't be any smell at all. So it won't be a health risk.