Owl monitoring project at local Reserves
Arranged by the Environmental Planner at Latrobe City Council, Brett McGennisken, owling expert Dr Rolf Willig visited the region to deliver a talk on monitoring owls, their habitat and behaviour and to conduct a sounding survey. This took place during a cold, clear evening at the Crinigan Bushland Reserve in Morwell and then at our Edward Hunter Heritage Bush Reserve in Moe where volunteers hoped to catch a glimpse or hear the call of an owl.
The focus of the survey was Victoria’s four large owls – the masked, sooty, barking and powerful owl, as well as the Southern Boobook.
The Powerful Owl (Ninox strenua) is the biggest of the ‘hawk owls’ and is listed as vulnerable in terms of the risk of extinction. It has a preference for dense gullies for places to roost and for breeding, large vertical tree hollows for nesting, and a good supply of prey mammals such as the Common Ringtail Possum. It also forages on forest margins for open country prey.
One limitation on its occupation of an area is the availability of suitable nesting sites. These are hollows of a size that typically takes around 150 years or more to form in eucalypts. Whilst the Reserve has quite a few large hollows, these may not be suitable for breeding powerful owls.
A powerful owl occupies a given home range of approximately 300 to 500 hectares and needs a possum a night to feed on, which would require a certain level of availability of said possums (and gliders) in an area. Pellets or castings (some birds regurgitate the indigestible parts of their meals- fur, bones, and so on) believed to have been produced by a powerful owl have been found in close proximity to the Reserve.
This time of year is ideal in which to undertake a sounding survey as the powerful owl is most responsive to playback between March and May, just prior to breeding season which commences in June.
Surveying for owls
There are various methods to find out which owls spend time in the area. The approach taken by Dr Rolf Willig involved a multi species sounding survey in three steps: silent listening, play back of the owl calls and spotlighting. Rolf had arranged the necessary permits needed for conducting a sounding survey for our evening.
After an uneventful sounding survey at Crinigan Bushland Reserve, we then made the trek over to our reserve at Moe. The moon had risen and the cold had increased and we were all thankful for our thick clothing. We chose a spot just off Borrmans Street, facing into the Reserve, over the gully.
After we had a period of silent listening, Rolf played a tape of owl calls, timed to allow us to listen for a response. We heard motor vehicles, dogs and a cow. There was some movement in the underbrush, perhaps from the local swamp wallabies. We then used spot lights to try to catch a glimpse of owls that may have been attracted to the sounds. We also heard the calls of frogs and wood ducks, and a potential boobook call at the end of the evening. But, we heard no owl sounds during the survey.
Our spotlighting found a ringtail possum.
While we did not hear or see owls on this night, sightings have been reported and reserves are ideal habitat for these amazing birds. We hope to talk Rolf into coming back to undertake further surveys.
- Breeds in winter; the larger the bird, the earlier the breeding commences
- Prey includes the ringtail possum, the greater glider, as well as magpies and kookaburras
- Tends to nip off the tail of its possum and to eat from the head down
- 60cm high and has distinct chevrons on the chest
- Likes dense foliage such as in blackwoods and pittosporum because it means it can keep out of sight of its prey
- Can take up to 40 minutes to respond to the calls from playback surveys
- Ideally, can best be found at dawn during breeding season when the male calls to the female that he has brought food, as well as dusk when they are starting to emerge from their roosting sites
- Breeds midwinter to spring
- Eats terrestrial and arboreal mammals; often insects during the non-breeding season
- 45cm high and has large ‘boggly’ eyes and striations in the colouring of its chest
- Breeding is from autumn to spring
- Eats small to medium terrestrial mammals and is the owl most likely to eat rabbits (it prefers the interface between cleared land and forest).
- 50cm high and has white ‘socks’
- Breeding is opportunistic but it tends to be autumn to spring
- Prey mainly includes terrestrial mammals but also arboreal
- 45cm high
- Breeds in spring, hopping on the nest near the end of winter
- Prey includes small birds and mammals, invertebrates, and house mice
- 35cm high
An owl’s prey can fight back. Rolf explained that brushtail possums can and do mob an owl, driving it off.
(You can hear the sounds owls make at the ‘Birds in Backyards’ site)
Birds is backyards (n.d.) Barking Owl basic information http://www.birdsinbackyards.net/species/Ninox-connivens
Birds is backyards (n.d.) Masked Owl basic information http://www.birdsinbackyards.net/species/Tyto-novaehollandiae
Birds is backyards (n.d.) Powerful Owl basic information http://www.birdsinbackyards.net/species/Ninox-strenua
Birds is backyards (n.d.) Southern Boobook basic information http://www.birdsinbackyards.net/species/Ninox-novaeseelandiae
DSE (2003) Action Statement: Sooty Owl Tyto tenebricosa http://www.dse.vic.gov.au/__data/assets/pdf_file/0014/103181/117_Sooty_Owl_2001.pdf
DSE (2004) Action Statement No. 91: Powerful Owl Ninox Strenua http://www.dse.vic.gov.au/__data/assets/pdf_file/0019/103177/092_powerful_owl_1999.pdf