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Powerful owl
The powerful owl (''Ninox strenua'') is a species of owl native to south-eastern and eastern Australia, the largest owl on that continent. It is found in coastal areas, the Great Dividing Range rarely more than inland. The International Union for Conservation of Nature
(IUCN) Red List of Threatened Species refers to this species as ''powerful boo-book'', however, this is not used as a common name in Australia.
==Description==
The powerful owl has a long tail and a small head, lending it an atypical silhouette for an owl and imparting a more hawk-like appearance than any other large owl. The protruding bill and distinct brow ridges enhance the hawk-like appearance of the species.〔Hume, R. (1991). ''Owls of the world''. Running Press, Philadelphia, PA. 1991.〕 The facial disc is ill-defined. The upperparts are a dark gray-brown colour, mottled and barred with whitish. The underparts are white with bold grey-brown V-shaped barring. The tail has six narrow white bars contrasting with grey-brown. This species has large yellow eyes, with greyish feathering down to the base of the toes and feet of a dull yellow color. They are aptly named, with very powerful and heavy claws. This owl is the largest species of the "hawk owl" group found in much of Asia and the Australasian region, all including in ''Ninox''. It can be considered, along with its sister species the rufous owl (''Ninox rufa''), as Australia's analogue to the ''Bubo'' genus.〔
This species measures in length and spans across the wings. Unlike in a vast majority of owl species, the male is slightly larger than the female on average. Most owls and raptors have reverse sexual dimorphism (RSD) whereas the powerful owl is considered to have normal sexual dimorphism (NSD) as do a majority of living (non-raptorial) birds. Body mass in males have been reported at , with 13 males averaging , while females can weigh from , with an average in 9 females of .〔() (2011).〕〔Hollands (2008) ''Owls, Frogmouths and Nightjars of Australia'', Bloomings Books, p318〕〔''CRC Handbook of Avian Body Masses, 2nd Edition'' by John B. Dunning Jr. (Editor). CRC Press (2008), ISBN 978-1-4200-6444-5.〕 Among all the owls in the world, the powerful owl is the ninth longest from bill-to-tail, the tenth heaviest and the eighth longest winged.〔''Owls of the World: A Photographic Guide'' by Mikkola, H. Firefly Books (2012), ISBN 9781770851368〕 Its body mass is about the same on average as the great horned owl (''Bubo virginianus'') but has a proportionately much longer tail and wings than that species. The wing chord length further illustrates slight sexual dimorphism in favor of the male, with the male measuring and the female measuring . The tail can be or more in length, the fifth longest of any owl with only the great grey (''Strix nebulosa'') and ural owls (''Strix uralensis'') having proportionately longer tails. As a relatively geographically restricted species, there are no subspecies and no known geographic variation in the powerful owl.〔Weick, F. (2007). ''Owls (Strigiformes): annotated and illustrated checklist''. Springer.〕 In comparison to the barking owl (''Ninox connivens'') it is much larger and lacks that species' white-spotted smoky-brown coloration on the upperparts and dark grey to rusty streaks on a whitish background on the underside. The other larger and relatively powerful owl found in Australia, the rufous owl, is not found in the same range in the wild so poses no identification problem.〔
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