Yeah, the birds are quick to dig out the natural instincts when they're back in the wild, even if their parents, grandparents etc were pets who lived inside for all of their lives!
That's what witnessed one of my relatives who lives near Paris. 12-15 years ago, there were a couple parakeets who nested in one of the parks in their suburb. They were bullied by the local species, pigeons, crows, you name it.
But over the course of the last decade, they have been increasing their numbers, and actually fought all of the other bird species for territory and
won!
And now, when I go there, it's rare to see a common pigeon or a house sparrow, but instead, you've got a Parakeet Reich that encompasses several blocks and only lets bright green feathers fly on their turf!