A crested flash of fire and a torrent of clear notes announce the cardinal, heart-throb of America's passion for birds. The blazing color, the ringing song - by male and female alike - seem like a tropical dream awakened, even on the coldest day. By any measure, the cardinal is America's most popular bird. We lavish tons of sunflower seed on the Northern Cardinal - state bird of seven states, vicar of countless backyards - yet do we really know this fiery bird? (50 mins.)