Here, in a song of very enduring popularity, is a particularly ludicrous example of fill-in lyrics, used desperately to make a rhyme -- "Here to stay is a new bird"?? What could they be thinking of, except what could be rhymed with "bluebird"? This must be high on any list of pitifully forced rhymes in highly popular songs. Incidentally, I've often assumed that this song is of U.S. origin, as it is certainly popular there. An origin in North America at least would tend to be pointed to because that is where bluebirds occur. There are three species of bluebirds situated so that all across the U.S. and southern Canada one would be where at least one of those species is found during at least some part of the year. This song might give the impression that they depart for the winter. While that is true for some northern parts of the U.S. and virtaully all parts of Canada where bluebirds occur, probably the majority of the area of the U.S. is within the winter or year-round range of at least one bluebird species. That would probably surprise many, in light of the view that this song seems to take!