Call is a relatively deep, resonating coo. Described phonetically as a monosyllabic "haoooo" (Gibbs et al. 2001), and as a two-syllable "hoo-hoooooo" (Chipley 1991) or "who-whooo" (Raffaele et al. 1998), rising in the middle and descending toward the end, occasionally without the first syllable. This author’s experience is consistent with that reported by Chipley (1991). A different call, described as a low-volume, rising then falling, "guttural croaking" call followed by a series of staccato notes, also reported by Chipley (1991). This call is reported as being associated with courtship, but its purpose is not understood.