This study was not done on parrots (no surprise there, right?) but it found that species that feed on seasonal fruits almost exclusively were more adaptable to switching food sources and I would think that you can extrapolate the findings to any of our companion fruit eating parrot species like all the phyrruras, for example. I know that I have found parrots like GCCs and sun conures very easy to convert to a diet with a large variety of fruits even though they are stubborn about eating their leafy greens.
https://www.sciencedaily.com/releases/2 ... 095230.htm