"small birds can get intimidated by larger birds, even if they are species that are known for being very peaceful and friendly. When they are confined in a tight space, small birds will not be able to escape their larger bird companions."
"Do not combine peaceful bird species with over-aggressive bird species."
"do not add a particularly flighty and nervous bird to mixed group birds"
birdscoo.com/care/housing-multiple-bird-species-together