Song: Advertising calls consist of a rapidly repeated call and song, both given in flight. Call consists of single, low frequency humming pulses. Song a combination of wheezy "gwarrr-gwarrr-gwarrr" and high twittering whinnies.
Sound: Monty Brigham (Bird Sounds of Canada); 1975 Oct 2; Canada, Ontario; Shirley's Bay, Ottawa; Adult; Primary Sound;