- Last updated:
- 20 Apr 2019
A few times a year we are woken up at night by the deep, resonant “hooo-hooo” call of a pair of Powerful Owls. Despite searching with torches we have never managed to see them at our place.
Just recently we were down in Sydney, staying in a suburb adjacent to a very large tract of coastal forest. On one of the nights we again heard the “hooo-hooo” call of the Powerful Owl. The next day it was twilight before I had a chance to walk into the bush again and already it was too dark to see much. At one point I thought to look up into the canopy of a tall eucalypt and thought I could see a symmetrical shape up there, darker than the bunched canopy. No witness, no torch, no camera!
By the time I had walked back and collected my witness and camera (no torch available) it was very dark but we found the tree again and Maureen confirmed the sighting and pointed out that there was a second large bird in the next tree. Through the camera view-finder and screen everything just looked black. Not to waste an opportunity I pointed the camera in approximately the right direction with Maureen alongside giving guidance: “more to the right – a bit more - no, a bit to the left” and so on. All up about 30 flash shots taken and only one was clear enough to prove it was indeed an owl.
The next morning we went back and could just make out an owl sitting in the same position (it was still quite gloomy in there) so we took a few more shots. Again, only one image was relatively clear and showed that overnight the Ring-tail Possum population had been depleted by one.
Powerful Owls, Ninox strenua, have a body length of 600mm or more with a formidable span of rounded wings up to 1400mm. As such they are by far our largest owl and a top nocturnal predator. The Powerful Owl is a carnivore, eating mainly medium to large tree-dwelling mammals, particularly the Common Ringtail Possum and the Greater Glider. It is estimated that these owls will eat between 250 and 350 possums in a year.
The owls hunt via hearing and sight, gliding through the trees, snatching prey from the canopy and mid-storey. The soft edges on the flight feathers allow completely silent flight. Roosting Brush Turkeys and Flying-foxes are taken this way. But terrestrial animals like rabbits, bandicoots and rats (even cats) are also hunted. Usually the victims heads are bitten off and eaten first. After digestion the remnants are disgorged as pellets composed of fur and feather. Small prey is swallowed whole.
There are nine species of owls on mainland Australia. Powerful Owls belong to the group (four species) called Hawk-owls, genus Ninox. (Ninox is a composite word meaning hawk-owl, strenua means vigorous). They are not related to the diurnal raptors but have similar features in strong, curved beaks and powerful talons for seizing and tearing apart their prey. They have relatively small heads especially when compared to the second group, the Masked owls (genus Tyto), which have large facial discs rimmed with short stiff feathers, like we associate with owls in general.
The double “hooo” call of the Ninox group especially that of the Powerful Owl is probably the only “traditional” owl call among Australian species. The calls of genus Tyto are shrieks, screeches and loud hisses. We think the calls we heard that led us to observe these magnificent birds were territorial calls in the lead-up to mating season, which is May to October. It is interesting that Neville W. Caley, the ground-breaking Australian ornithologist, in all of the many editions of his iconic book “What Bird Is That” (the first field-guide of Australian birds) describes the call of the Powerful Owl as a “hideous scream”. This is not correct.
Powerful Owls pair for life. They utilise a number of roosting trees, generally tall eucalypts. For nesting they require a large, deep hollow very high in an old tree, where the female lays and incubates one or two eggs. The male’s task is on-going food supply for the female and later also for the chicks which are hatched in about five weeks and fledged in another eight weeks or so. The same hollow is used every year. Such large birds also require an extensive hunting range of up to 1000 hectares per pair. Habitat is varied but favours wet and dry sclerophyll forests, also rainforests and coastal forests The Powerful Owl has a distribution range across south-eastern Australia, mainly east of the Great Dividing Range from about Mackay to the southern South Australia and Victorian border.
Article by Kon Hepers