What is a galah thinking?

The noise is the point. Galahs are flock birds and the flock is the whole survival strategy - more eyes on the sky, more warning before a hawk arrives - so the calling is constant contact, everyone confirming where everyone else is. A flock breaking cover at dusk is not chaos, it's a headcount.

They also mate for life and hold the same nest hollow for years, which is a long time to be that loud in one postcode. And that pink-and-grey combination is not decoration - the grey back disappears against dead timber, and the pink underside vanishes into a sunset sky when they're overhead. An extremely conspicuous bird that is, at both ends of the day, quite hard to see.