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
Australasian wren from such pairings. Males of several species pluck petals of conspicuous colours and display them to females for reasons unknown. The song of fairywrens is pleasant and complex, and at least two species (superb and splendid) possess, in addition to the alarm calls common to – and universally understood by – most small birds, another vocalization used when confronted by predators. This, termed "Type II Vocalization," is song-like and used when confronted by calling butcherbirds, and sometimes other predatory birds. Its purpose is, however, unknown; it does not seem to be a warning call. Australasian wren The Australasian wrens are