Mistletoebirds inhabiting open eucalypt forest at Ebenezer, near Windsor, New South Wales, vocalized maximally from about 15 minutes before, until two hours after, sunrise. This contrasted with most other species whose peak vocalizations were before sunrise. There was negligible singing through the day, as in other species. An annual influx of birds into the areas of flowering, then fruiting, mistletoe (Dendrophthoe vitellina) was documented annually in late November--early December over five summers using levels of territorial song. Bird numbers were high during years of good mistletoe abundance and productivity, low in the poor years that followed plant die-off. Seasonal movements relative to the berry production cycle in mistletoe are confirmed as a major adaptation in Mistletoebirds.