Many birds kept as pets, including doves, parakeets, and lovebirds, enjoy living in pairs for companionship. The smallest bird egg belongs to the hummingbird and is the size of a pea. The largest bird egg, from which the ostrich hatches, is the size of a cantaloupe. The penguin is the only bird that can swim, but not fly. It is also the only bird that walks upright. Source
Hummingbird credit
Birds facts Penguins credit
