Aves

Companion birds range from the 30-gram budgerigar to macaws that outlive their owners, and almost all of them are, cognitively, wild animals a handful of generations from the flock. That means intelligence that needs daily work: parrots solve puzzles at the level of young children, learn dozens to hundreds of words, and without stimulation invent their own occupations — usually loud or destructive ones. The non-negotiables: the biggest flight cage you can house (width beats height for most species), daily out-of-cage time in a bird-proofed room, a varied diet where formulated pellets and vegetables displace seed mixes (an all-seed diet is slow malnutrition), and absolutely no Teflon fumes, avocado or scented candles — bird lungs are extraordinary and extraordinarily fragile. A single bird bonds hard to its human and needs hours of company; a pair keeps each other sane when you're away.