PSITTACIFORMES: Psittacidae
Polytelis anthopeplus
An unusual chattering sound, described as a "distinctive, mellow, rolling, deep-in-the-throat 'quarrark quarrark'" in Michael Morcombe's book, led me to finally find some Regent Parrots which promptly flew away as soon as I found them.
Fortunately one went only a few trees away and I was able to get some photos.