This is going to be a shorter post simply because there’s just not that much research out there on the subject of parrots kept in isolation vs those kept with other members of their species.
The few pieces that are out there are pretty clear that social isolation is not good for Amazons and African greys (the two species that have been most researched).
Birds are routinely
denied two of their most fundamental natural behaviours:
flying and socialisation. It has been suggested that the
denial of these activities can cause both physical (Graham
1998) and behavioural abnormalities in captive parrots (van
Hoek & ten Cate 1998; Garner et al 2003b; Meehan et al
2003a, 2004; Meehan et al 2003b). Parrots kept as pets are
often housed alone or in pairs in small cages incapable of
accommodating flight (van Hoek & ten Cate 1998)
The biggest research on the subject came from UC Davis’s studies with Orange Winged Amazons in the early 2000s. Once upon a time, there was a great summary posted online, but it appears to have disappeared. For now, this is the best link I can find — https://www.infona.pl/resource/bwmeta1.element.elsevier-a899eac9-1f3a-3939-8ba2-114f787b4730:
Isosexual pair housing resulted in a more active and diverse behavioral repertoire, eliminated the development of stereotypy and reduced fear responses to novel objects without imparting significant risk of illness and injury or jeopardizing the ability of parrots to relate positively with humans. Thus, it appears that pair housing can significantly improve environmental quality and positively affect the welfare of captive parrots.
And finally, some more recent research on African greys. From Science Daily:
Scientists at the Vetmeduni Vienna examined the telomere length of captive African grey parrots. They found that the telomere lengths of single parrots were shorter than those housed with a companion parrot, which supports the hypothesis that social stress can interfere with cellular aging and a particular type of DNA repair.
If you know of more research for or against pair keeping, please leave details in the comments!
Next up will be ‘setting yourself up for success’ and finally ‘introducing more challenging parrots’.