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 boobook" in 1801, writing about it in English, before giving it its scientific name, taking its species epithet from a local Dharug word for the bird. The species description was based on a painting by Thomas Watling of a bird—the holotype—in the Sydney district in the 1790s. John Gould described "Athene marmorata" in 1846 from a specimen in South Australia; this is regarded as a synonym. German naturalist Johann Jakob Kaup classified the two taxa into subgenus "Spiloglaux" of a new genus "Ieraglaux" in 1852, renaming "S. boobook" to "Ieraglaux (Spiloglaux) bubuk". In his 1865 "Handbook to the Birds of