No, it is not a fact that lovebirds, parakeets and cockatiels will bond only with one other bird during their lifetime. In the wild, cockatiels do tend to form closer pairings than do other birds. These mates may remain bonded for multiple seasons, (but may occasionally "stray").

It is likely that a lovebird and a parakeet would accept another partner easier than a cockatiel would, should their mate pass away. However, if the bird is young, the cockatiel would eventually accept another mate in most instances. Cockatiels do often live for decades.

Birds that form bonded pairs for multiple seasons that may have difficulty accepting another mate include doves, eagles, swans, geese. owls, large parrots, etc.. However that is not to imply that they will not bond with another mate, only that they may have difficulty doing so. Best wishes. -PetCaretaker

Thank u.