Christmas boobook lores and throat, yellow eyes, legs and feet. It is approximately 26–29 cm in length and 130-190 grams in weight with the female slightly larger than the male. The double-noted hoot, "boo-book," has a clucking quality with the second note usually lower in pitch. The begging call of juveniles is a high-pitched trill. Vocalisations are similar to those described for the Southern Boobook "N. novaeseelandiae" and include individual variation in advertisement calls. This may be useful in estimating owl densities as radio-tracking can be impractical in some terrains. A recording, courtesy of Richard Hill and Owl Pages http://www.owlpages.com/sounds/Ninox-natalis-2.mp3 Its natural
Southern boobook treated Australian and New Zealand boobooks, along with several taxa from Indonesia and Papua New Guinea, as one species—"Ninox novaeseelandiae"—with 16 subspecies. In his 1968 book "Nightwatchmen of the Bush and Plain", Australian naturalist David Fleay observed that the boobooks from Tasmania more closely resembled those of New Zealand than those from mainland Australia, though he followed Mees in treating them as a single species. The southern boobook was split from the Tasmanian boobook and morepork in volume 5 of the "" in 1999, though several authors, including Australian ornithologists Les Christidis and Walter Boles, continued to treat the three