Unfortunately, not on parrots but on chickens BUT the findings are VERY interesting and I would bet perfectly extrapolatable to parrots. Just a little 'trailer': it says that birds that have a more natural and complex environment and the ability to decide on their own cope with stress much better [more 'optimism' and more dopamine, the reward and pleasure neurotransmitter] now, if this is how chickens [which have been domesticated for over 10,000 years] react, imagine what this means when applied to parrots!!!!
https://www.sciencedaily.com/releases/2 ... 112219.htm