It is ten years since the Powerful Owl Project was initiated under the auspices of Birdlife Australia. This highly successful project aims to involve the general public in discovering information about the Powerful Owl population, their location and behaviour and carry out research into their health and habitat needs.

The intrepid citizen scientists have far exceeded the original expectation of finding 50 territories in Greater Sydney and surrounds; the total now is over 250. Their observations have contributed enormously to the understanding of the ecology of the Powerful Owl in the urban environment.

Here are some extracts from the newsletter that documents the experience of the last 10 years or so.

Breeding success

It’s been a good breeding season for our urban owls, with 95 successful breeding sites and 157 chicks fledged, up from 121 chicks fledged last year. It’s been a good year for double chick clutches, with 65.3% of clutches having two chicks, up from 39.5% last year. The table below gives an overview of the breeding season stats for the past few years.

Research into nesting hollows

We know Powerful Owls need large tree hollows to breed, but we don’t know much about the environmental conditions inside the hollows where successful breeding takes place.

In March 2021, data loggers were installed in 11 known Powerful Owl nesting hollows across the Sydney Basin, funded through Cumberland Bird Observers Club. The data loggers measured the temperature and humidity levels in the hollows during the breeding season and were retrieved again in November. A huge thank you to Kai Wild, arborist and environmental campaigner, who installed and retrieved the loggers.

Powerful Owls successfully use both dead trees and live trees for nesting. We had hoped to install the data loggers in a representative sample of each, but the dead trees proved too dangerous to climb.

We are rapidly losing our old, hollow-bearing trees through land clearing, bushfires, drought, safety concerns and natural attrition. A hollow suitable for a Powerful Owl to breed in takes 150 to 500 years to form. At current rates of loss, scientists have estimated that in 95 years there will be no suitable tree hollows left in the urban space that can accommodate the breeding of Powerful Owls.

The results of the analysis will be available in January 2022. They’ll help inform land management decisions around the retention of hollow bearing trees and help guide attempts to design artificial nesting structures for Powerful Owl. To date, all attempts have been met with owly disdain, other than on one occasion where the owls successfully fledged a chick from a nest box but have not returned to it in subsequent seasons.

Mortality

Sadly there were 82 death and injury events recorded in 2021. 85% of these birds were either killed outright or died in care due to their injuries. For all reports we received we collated all the information we could on where the bird was found, what the physical signs were and, where possible, bodies were collected and necropsied.

These numbers are, sadly, more than double that of 2020, largely due to a doubling in reported cases of motor vehicle accidents and an increase in death or injury from animal attack or from unknown cause. Of course, as people become aware of the ability to report incidents then of course reporting to us increases so it is difficult to determine just yet whether these events are increasing, or people are simply more aware of how to report them.

What we do know though is that motor vehicle accidents continue to be the largest single cause of death and injury in our urban owls with 39% of reported injuries/deaths in 2021 and 50.4% of injuries/deaths in our records since 2012.

What to do if you find an injured or dead owl

If you find an injured Powerful Owl do not attempt to rescue the owl yourself, for the safety of both yourself and the owl. The rescue of raptors requires specialist training and handling.

Assess the environment for any potential danger to yourself. Check if there are any immediate threats to the owl. Take note of your location (GPS coordinates or address). Then call a specialist wildlife rescue organisation and they will talk to you, assess the situation, and decide what action needs to be taken.

If you’re in the Sydney Metropolitan Area, please call either of the following (both available 24 h day, every day of the year):

• Sydney Wildlife Rescue on 9413 4300
• WIRES on 1300 094 737

If you find a dead Powerful Owl, please let someone know, as knowing how many Powerful Owls are dying, and where and why they are dying, is important for our understanding of how to support the survival of the species.

Rodenticides

The use of rodent poisons is a major concern for the survival of all raptor species. Of particular concern is what are called second-generation anticoagulant rodenticides (SGAR). These are rat poisons with the active constituents of brodifacoum. Studies of dead Powerful Owls has shown that we can add Powerful Owls to the more than 40 Australian animals and bird species that are poisoned by these products.

There is more work to come, but early results from our research are alarming and is why we will be pushing forward with this research and actively campaigning for the removal of these second-generation rat poisons from public sale. From our first batch of testing we have found:

• 37 of the 38 samples showed an anticoagulant rodenticide was present.
• The most common rodenticide present was brodifacoum. Brodifacoum is a SGAR, the most persistent anticoagulant rodenticide registered for use in Australia, and is the most common one used in rat poisons available on hardware and supermarket shelves.
• Nearly 60% of Powerful Owls tested had levels high enough to cause impairment. This likely puts these birds at greater risk of other threats such as being hit by vehicles – the leading cause of death we are seeing in these Sydney birds.
• An additional 10.5% had AR levels high enough to kill the bird outright.

How you can help

As the largest hardware retailer, Bunnings can be leaders in the market by removing a huge source of poison from their shelves and instead providing consumers with alternatives that are just as effective.

Sign our petition, but also use our Bunnings finder to (politely and respectfully) call your local Bunnings store and let them know you are concerned about this issue. We even have a script for you to use.

Powerful Owl Coalition

STEP is a member of the Powerful Owl Coalition, a group of northern Sydney environment groups that aims to promote improvement in habitat for Powerful Owls. We have been working with Dr Beth Mott the head of the project for the past five years. Sadly she has moved to another job. We greatly appreciated her extensive knowledge and assistance with our work.