Powerful Owl Study on Oatley Owlets

Powerful owlet OatleyMatt Mo and David Waterhouse OFF members have just published  their observations on a pair of Oatley Owlets in a paper in Australian Field Ornithology.
This paper extends previous observations of behavioural development in Powerful Owl Ninox strenua fledglings. The study combines a near-daily visual monitoring program on a pair of owlets in Oatley, suburban Sydney, New South Wales, with corresponding pellet analysis.
The fledglings were initially fed on possums, fruit-bats, birds and insects, and first demonstrated independence by disassembling carcasses by themselves. By October, they apparently mimicked the adults’ strategy for capturing insects, and began to chase birds and bats. Behaviours thought to be part of honing their hunting skills—including tearing and ferrying strips of bark, foliage-snatching, and swooping at animals on the ground—were recorded. Such actions intensified during a period when the adults were mostly absent in November and December.

Microbat Predation on Mosquitoes

MicrobatDr Leroy Gonslaves studied the diet of microbats that live on the Central Coast for his PhD. His study area in Empire Bay has large areas of saltmarsh, which can support huge numbers of mosquitoes at different times of the year. Apart from nuisance biting, these particular mosquitoes have the potential to spread diseases such as Ross River and Barmah Forest viruses – which can cause rashes, fever and rheumatic pains. To See Powerpoint of Talk Click Here ( 75MB) Dr Gonslaves has also surveyed 56 Sites across Sydney for Microbats. Click here to see Sydney Morning Herald article

Herpetofauna of Lime Kiln Bay

A5. Lime Kiln Bay wetlandsMatt Mo’s latest publication on The Lime Kiln Bay Wetland provides the first comprehensive description of the amphibians and reptiles at the site from observations made between 2006 and 2014. Twenty-three species were detected: six frogs (Hylidae, Limnodynastidae, Myobatrachidae), one freshwater turtle (Cheluidae), 12 lizards (Agamidae, Carphodactylidae, Scincidae, Varanidae) and four snakes (Colubridae, Elapidae, Pythonidae).

Published in the The Victorian Naturalist 132 (3) 2015, 64–72)


The best ways to beat the bite of blood thirsty mosquitoes

Dr Cameron Webb was our first speaker for 2015 regaling the audience of 60+ members and guests with warm-blooded facts and anecdotes on mosquitoes and diseases associated with these pesky ankle biters. He has provided us some useful way to beat the bites.

cameronwebb_mosquitoes_theleaderMosquitoes found around the Georges River region are more than just nuisance-biting pests. Mosquito-borne pathogens, in particular Ross River virus, are regularly detected and there have been cases of human illness in the local area too. There is no mosquito control in the local wetlands so individuals need to take steps themselves to avoid mosquito bites. Long sleeved shirts, long pants and covered shoes will provide a physical barrier against mosquito but the use of topical insect repellents will be important too. There is a range of cheap, safe and effective repellents available in Australia. A repellents should be approved by the Australian Pesticides and Veterinary Medicines Authority (APVMA) who test for effectiveness and safety. There’s over 100 insect repellent formulations currently registered while dozens more unregistered repellents are commonly found for sale at various stores, markets and via online retailers. The best repellents contain either DEET or picaridin as these chemicals have been repeatedly demonstrated in testing to provide the longest lasting protection against a range of biting insects. Many reviews of the literature have shown that, considering the widespread international use of these repellents, there are very few adverse health impacts reported (keeping in mind that their use has probably saved many live from potentially fatal illnesses such as malaria or dengue).

By Paul Zanetti By Paul Zanetti

There are other types of repellents available. The most common are plant-based products such as tea-tree, eucalyptus, lavender, cat mint and peppermint oils. These repellents vary in their effectiveness but generally provide less protection than DEET or picaridin and if you prefer to use these types of repellent, it is important to remember that they’ll will need to be reapplied more frequently to provide comparable protection. mossie It isn’t all about choosing the right repellent, to prevent bites you’ve got to use it correctly. Regardless of formulation, there must be an even and complete cover of all exposed skin otherwise mosquitoes will find a way through. Reapplication is required after swimming or physical activity. Spraying repellent on clothes or giving a dab “here and there” isn’t going to provide protection. Although mosquito repellent patches and wrist bands have been registered they won’t “whole body” protection against mosquito bites. Using mosquito repellents is the best way to reduce the risks of mosquito-borne disease. If you’re out and about around the local wetlands and bushland areas, it is important to take measures to avoid mosquitoes so make sure you pack a tube of insect repellent in your bag this weekend. For more information see the recent article at The Conversation “Chemical or natural: what’s the best way to repel mozzies?” Dr Cameron Webb – Department of Medical Entomology, University of Sydney and NSW Health Pathology. Email: cameronn.webb@health.nsw.gov.au Twitter: @mozziebites  CLICK HERE TO SEE BLOG FOR MORE INTERESTING INFORMATION :

Dr Cameron Webb on Mozzie Menace

cameronwebb_mosquitoes_theleaderMosquitoes been bugging you this summer ? Stop those sleepless summer nights! Come hear Dr Cameron Webb, Medical Entomologist with the University of Sydney and Pathology Westmead Hospital, speaking on mozzies and mosquito-borne disease at the next  Oatley Flora and Fauna Society meeting Feb 23rd (Mon) 7.45pm  at Uniting Church Hall Fredrick St,  Oatley. For more information on Dr Cameron Webb see his blog at http://cameronwebb.wordpress.com  

Rain Water Harvesting in Oatley

Jim Vickery , OFF member and retired Environmental Engineer, spoke on this topic at the 27th Oct meeting. Jim is determined to capture as much life- giving rain falling on his roof as possible by storing it in water tanks around his home. This reduces his reliance on town water supply and the erosive impact of excess storm water on our local streams. He provided guidelines and graphs showing the relationship between tank size and roof area based on rainfall records. In drier times, the Reliable Draw[water drawn every day without emptying tank ] is between Average Summer and Dry Winter levels shown in this chart. It is a useful guide relating storage volume and roof catchment area. A 2000L tank provides 50 100 L/day [if catchment is 100 sqm or more], sufficient to supply a
toilet in a small household and some water for the garden. A 6000L tank needs at least 200 sqm of catchment to supply water to a washing machine, toilet, and garden. Techniques for the collection, storage and delivery of rainwater were reviewed along
with uses for the water that overflows the tank. Jim runs his excess water into a swale in his backyard providing a bog that can recharge the water table. Running excess into a pond is another excellent method of harvesting rain water.
Rainwater tank installation guidelines:
  • Determine your daily need for rainwater.
  • Determine the size of your available roof catchment area.
  • A 2000 L tank will provide 50 to 100 L/day from a 100 sq m or larger roof.
  • A 6000 L tank or larger is necessary for supplying a washing machine or something similar. If the roof catchment area is greater than 200 sq m then the tank is less likely to empty out during dry periods .



OFF Library

the-biggest-estate-on-earthThe Society has purchased a number of books which are available for loan to OFF members.  Available at the back desk at Monday meetings.

Titles include :

  • The Biggest Estate on Earth (Bill Gammage) – investigates the land management of Aborigines.
  • A History of the Blue Labyrinth (Bruce Cameron) – a beautifully produced book with lots of photos and many references to our former Treasurer Harry Whaite
  • Sustainable House (Michael Mobbs) – what one person has done to be self-sufficient in energy, water and waste disposal in his Sydney house.
  • Sustainable Food (Michael Mobbs) – the sustainable use of water and energy associated with growing and processing food.
  • A Natural for World Heritage (Geoff Mosley)- the argument for granting World Heritage Listing for Royal National Park. The Green Corridors of Southern Sydney (NPA Southern Sydney) – a DVD outlining the importance of protecting the green areas south of Sydney,

Georges River Studies Helps River Conservation

Ecosystem Guidelines for the Conservation of Aquatic Ecosystems of the Georges River Catchment: A Method Applicable to the Sydney Basin Click here for pdf of study

For waterway managers the conservation of freshwater streams in Australia is commonly
underpinned by comparing water quality data with default ANZECC water quality guidelines.
However distinctive conditions found within many streams of the Sydney basin render a number of the
default guidelines not suitableand prone to misinterpretation. In this study we draw on a three year
monitoring program and follow the framework recommended by the ANZECC guideline to develop
a catchment specific approach for the conservation of aquatic ecosystems for the Georges River
catchment. In addition to the ‘common’ set of water quality guidelines we include values for a
selection of ionic parameters and guideline values for aquatic macroinvertebrate communities, riparian
vegetation condition and catchment imperviousness. The study revealed three distinct
patterns of ecosystem disturbance and water quality characteristics that corresponded to the level of development across the catchment from reference forested areas through to highly urbanised centres.When compared to non-urban reference sites streams with greater than 5% impervious surfaces showed
emergent signs of ecosystem degradation while those with >19% imperviousness had highly degraded
water quality, macroinvertebrate communities and riparian vegetation.Based on the results of this
study, we recommend two sets of regionally relevant ecosystem and water quality guidelines, one for
the conservation of streams with high ecological value that would apply to waterways with minimally
disturbed catchments and the other to apply to urban streams and stream restoration projects.
Although the focus of this paper is the Georges River catchment, the approach developed in this study
can be easily applied to other urban catchments within the Sydney Basin

Is Catchment Imperviousness a Keystone Factor Degrading Urban Waterways? A Case Study from a Partly Urbanised Catchment (Georges River, South-Eastern Australia


The extent of catchment impervious surface is recognised to be an important factor associated with the condition of urban freshwater streams. We tested the hypothesis that the degree of catchment imperviousness predicted the relative ecological condition of freshwater reaches within the network of streams and rivers in the partly urbanised Georges River catchment in temperate south-eastern Australia. The 2-year study involved two spring and two autumn assessments of water quality (chemical and physical) and ecological condition, using benthic macroinvertebrates, riparian vegetation and calculation of catchment imperviousness. The study revealed that highly urbanised streams had strongly degraded water quality and macroinvertebrate communities, compared to clean non-urban reference streams. We found three clear groups of sites with varying degrees of ecological condition, being categorised according to the level of catchment effective imperviousness (low <5.0 %, moderate = 5.0–18.0 % and high >18.0 %). Water pollution also varied according to these categories. A combination of two water chemistry attributes (total nitrogen and calcium), along with catchment imperviousness and riparian vegetation condition, were identified as being the factors most strongly associated with variation of macroinvertebrate communities. Based on our results, we recommend that protection of the ecological condition of streams should focus on not only water quality but also include catchment imperviousness and riparian vegetation condition.

The influence of concrete on the geochemical qualities of urban streams


The geochemical signature of freshwater streams can be used to determine the extent and nature of modification to stream water geochemistry due to urban development. This approach used the Gibbs (1970) diagram as a model for evaluation of changes to ionic composition linked to urban development. In this multi-year study, the geochemistry of 21 waterways in the Georges River catchment, Sydney, were monitored and compared with the level of urban development as measured by sub-catchment imperviousness and directly connected imperviousness. The results reflect a strong relationship between the intensity of sub-catchment urban development and stream geochemistry. All major geochemical attributes increased with escalating levels of urban development. The largest increase was for bicarbonate, which increased 18 times from a mean of 6.4 mg L–1 at non-urban streams to a mean of 118 mg L–1 at urban streams. Similarly, mean concentrations of calcium increased by 14 times (from 2 to 27.9 mg L–1). Mean salinity was enriched in the most urban streams, compared with non-urban streams, by more than 6 times. We attribute this, in part, to the influence of urban geology, notably concrete stormwater infrastructure. Changes in stream geochemistry due to urban development are an important element of the urban stream syndrome.

Oatley Owls the First to Fledge Chicks

Matt_Bev_Peter_owlphotoUnderstanding the habitat requirements of breeding Powerful Owls (Ninox strenua) in Sydney is an important step in improving species management in urban areas. A Birdlife Australia project focusing on the population dynamics, breeding success and requirements of owls in the Greater Sydney Area is in its third year. In addition, the owls of the lower Georges River are under surveillance for a study led by Chris Lloyd, who is speaking to the Society in September this year.

For reasons that are still unknown, the breeding season in 2014 has been later than previous years, with many breeding pairs commencing nesting in July. Two breeding pairs in Oatley and surrounds are leading the charge, having laid eggs in June. In an achievement for the St George area, chicks from these owls have been heard at both sites, and seen in one. According to David Bain of Birdlife Australia, these are the first of the season.

The photograph is of the juvenile owl at one of the Oatley sites on the day after fledging.

Matt Mo, Bev Pedder and Peter Hayler 18 August 2014

REMINDER – Chris Lloyd will speak on the Changing ecology of the Georges River and Powerful Owls at next Oatley Flora and FAuna Soc. meeting on Monday 22 September.


The Economics of Mining

On Monday 11 August OFF members attended a seminar on debunking myths on the economics of mining. Coal Mines and Gas fields are approved largely on the basis of the claims made about jobs and economic benefits. However, two speakers from  The Australia Institute enlightened  the audience on the fact 0f who benefits and who bears the costs of the mining industry in the NSW economy.

Two papers summarizing the information were distributed:


State govt assistace to mining industryOFF obtained a copy of Mining The Age of Entitlement -

State governments are more usually associated with the provision of health, education and law enforcement than industry assistance. So it might surprise taxpayers to learn that state government assistance for the mineral and fossil fuel industries consumes significant amounts of their money. This paper details the value of state revenue that would otherwise have been available for increased vital public services – for example, more teachers, nurses and police.

by Richard Denniss, Roderick Campbell and Richard Denniss