Whether they have any extant function or not, they have lost their former function and in that sense they do fit the definition of vestigiality. Vestigial structures are often called vestigial organs, although many of them are not actually organs.
There are quite a few birds famous for doing ritualized mating dances, so I would only list 5: The Red Capped Manakin, The Black-footed albatross, The Western and Clark's grebe, The Superb bird of Paradise, & The Victoria's riflebird.
Our two cowbirds species, the Brown-headed and the Bronzed, are the only birds in North America that are completely dependent on other birds to raise their young. Therefore they are described as obligatory nest parasites.ur two cowbirds species, the Brown-headed and the Bronzed, are the only birds in North America that are completely dependent on other birds to raise their young. Therefore they are described as obligatory nest parasites.