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 Hydrographic Society and gas industries, particularly off the north west coast of Western Australia and coal export facilities in Queensland have required a considerable increase in the provision of accurate and up to date hydrographic information. The attendant increase in trade, for example, has made improved navigation through sensitive area, such as the Great Barrier Reef critical. Hydrography also plays an important role in national security, border protection and humanitarian support. The Australasian Hydrographic Society endeavours to represent all interests in these domains. The Australasian Hydrographic Society consequently "aims to serve anyone with an interest in the science (and art)" of hydrography,