Galahs are highly socialised and live in large groups. I certainly want to believe they take pleasure in flight, and I love seeing them fly above the Brisbane River where I live but I am drawn to observe they are also probably subject to social pressure like flocking behaviour, peer and dominance establishment, and threat of exclusion. Reduction in stress hormones would be normal in an animal conforming within it's group and not being bullied or put under stress. Still there's a determinism in poo testing I like. It's pretty black and white.

Also, these were presumably cage bred. Not sure I'd generalise from this cohort to the wild.

More work to be done I'd say. The evidence of crows and others repeatedly gliding and swooping from roof ridge to eves and back again suggests they ideate some sense of purpose in flight, and it looks playful. They do similar things not flying, which definitely look play like, so it seems reasonable to assert the flight which simply displays an ability to fly with no other purpose is done for pleasure as much as any other reason.