You haven't seen anything that attracts birds, like an almond orchard! The parrot species in particular, will literally try everything to get to them - and birds are a lot more clever than many people think. I'd place many birds as smarter than the smartest dog.
Shooting doesn't work, the birds merely watch out for firearms and human shapes, and shot birds are simply replaced by other birds from further away who haven't realised there are shooters associated with the food trees.
Constant harassment of the birds is the best form of defence, they give up after regular harassment, and go elsewhere to find their food.
The harrassment can take multiple forms, and a variety of harassment forms keeps them on edge.