I have had a Blue and Gold macaw Parrot for 21 years.When the temps get up over 75 degrees I like to take him out to the deck and let him talk and visit with people that walk by (I live on a corner and have a raised deck).
This year I have resisted taking him out because of the Bird Flu. I live in Chicago so no water foul are encountered only the usual wild birds for our area.

For you Bird experts; When would be a safe time to take the bird outdoors on a perch?

OK, bird flu os contagious only of you allow them to come in contact with a sick bird.
As long as he's just out in the sunshine, he's safe.

Never worried about it in the 30+ years I’ve kept parrots. Be responsible, don’t let your baby interact with the Wild ones. Clean up his location before perching him outside. You’ll be fine.