Wild budgies have no easy life. They live in Australia's "Outback", that's what they call the central part of the country, where there's little or no rain during the year.
Still, these birds have what it takes to survive in this barren place.
This is one of the reasons:
Appearance (I'm hereby referring to one of my earlier posts)
Potentially, there are about 20 million different possible colour combinations for aviary budgies. But the wild budgie is green. Any significant variation on this would make the bird stand out in the crowd, so it would become an easy target prey for hawks.
One more reason: they are absolute acrobats in the air. Although there can be over one thousand budgies in one flock, they will never collide. Wild budgies are quite small, slim and athletic. Their tiny form and athleticism make them difficult to catch.