Can you get some clear plastic strips, and hang them down from the roof? If you space them out a little it shouldn't trap too much heat.
If your electrically inclined you could maybe get a motion detecting frog, and rig it up to a horn. The neighbours (and you) might not like it though.
If you think its parrots, I wouldn't suggest getting a cat, but if its india myna birds or something, then get a cat.