powerful owl project in southeast queensland progress report

Powerful Owl Project in southeast Queensland

Progress Report

October 2020

Powerful Owl Project in southeast Queensland

Progress Report

Rob Clemens, Larry Chen, Callan Alexander, Susan Fuller

October 2020

Citation

This publication should be cited as follows:

Clemens, R., and Chen, L., Alexander, C., Fuller, S. (2020) Powerful Owl Project in southeast

Queensland, Progress Report. Unpublished report. BirdLife Southern Queensland, Brisbane.

Copyright © BirdLife Australia

This document is subject to copyright and may only be used for the purposes for which it was

commissioned. The use or copying of this document in whole or part without the permission of

BirdLife Australia is an infringement of copyright.

Disclaimer

Although BirdLife Australia has taken all the necessary steps to ensure that an accurate document has

been prepared, the organisation accepts no liability for any damages or loss incurred as a result of

reliance placed upon the report and its content.

Cover image: Powerful Owl Ninox Strenua, by Amanda Robertson.

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Table of Contents

Acknowledgements ........................................................................................................................................................ 5

Executive Summary ........................................................................................................................................................ 6

Introduction .................................................................................................................................................................... 9

Objectives ..................................................................................................................................................................... 11

Powerful Owl distribution in southeast Queensland ................................................................................................. 12

Powerful Owl observations .............................................................................................................................. 12

Figure 1. Map of Powerful Owl records in southeast Queensland at 25 km2 resolution................................... 14

Other Nocturnal bird locations in southeast Queensland in BirdData database ............................................. 14

Engagement.................................................................................................................................................................. 16

Number of people involved .............................................................................................................................. 17

Volunteer engagement and feedback .............................................................................................................. 20

.......................................................................................................................................................................... 20

Rat Poison Campaign ........................................................................................................................................ 23

Media attention .................................................................................................................................................. 24

Stakeholder Engagement ................................................................................................................................. 25

Acoustic Monitoring ..................................................................................................................................................... 26

QUT Acoustic Monitoring ................................................................................................................................. 26

Current Progress: ................................................................................................................................................ 26

Additional deployments ................................................................................................................................... 27

Impact of summer 2019/20 bushfires on forest owl habitat .................................................................................... 29

Methods .............................................................................................................................................................. 29

Results ................................................................................................................................................................. 31

Two research papers submitted to Sunbird in 2020 .................................................................................................. 33

Review of conservation status of three forest owls ................................................................................................... 35

Powerful Owl Ninox Strenua ............................................................................................................................ 37

Overview .............................................................................................................................................................. 37

Infraspecific taxa ................................................................................................................................................. 37

Range .................................................................................................................................................................. 37

Abundance .......................................................................................................................................................... 37

Ecology................................................................................................................................................................. 38

Monitoring ........................................................................................................................................................... 39

Threats ................................................................................................................................................................. 39

Australian Greater Sooty Owl Tyto tenebricosa tenebricosa ........................................................................... 41

Overview .............................................................................................................................................................. 41


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Range ................................................................................................................................................................... 41

Abundance .......................................................................................................................................................... 41

Ecology................................................................................................................................................................. 42

Monitoring ........................................................................................................................................................... 42

Threats ................................................................................................................................................................. 42

Southern Masked Owl Tyto novaehollandiae novaehollandiae ....................................................................... 44

Overview .............................................................................................................................................................. 44


Range ................................................................................................................................................................... 44

Abundance .......................................................................................................................................................... 44

Ecology................................................................................................................................................................. 45

Monitoring ........................................................................................................................................................... 45

Threats ................................................................................................................................................................. 45

Comparisons of forest plots near Powerful Owl breeding and random locations ................................................... 47

Methods .............................................................................................................................................................. 47

Results ................................................................................................................................................................. 48

Literature Cited ............................................................................................................................................................ 50

Appendix A. Powerful Owl Project Volunteer Survey Results 2020 ................................................................. 57

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Acknowledgements

We would like to thank the over 500 volunteers who have signed up to the project, and

special thanks to Jasmine Zeleny and Matt Wright. This pair of seasoned owl experts

have helped deliver workshops, and have been a huge help in the field, providing a large

amount of data on owl distributions.

This year we would like to thank Laura Ferris and Darcy Brady who helped tremendously in

the field this year, and worked on the project as student placements from the University of

Queensland.

We would like to thank QUT for their partnership and support on the Queensland

Government grant.

We would like to thank all those who have helped with the project, and would especially like

to thank the following people for their contributions: Alicia Allan, Claire Anderson, Robert

Auld, John Baldry, Ed Blackwood, Julie Cahill, Rodney Appleby, Anthony Baker, Tyde Bands,

Josh Bowell, Nick Bradsworth, Nick Bricknell, Leah Burns, Brett Coleman, Jennifer Davis, Alexis

Dawson, Stephen Debus, Lesley Eagles, Andrew Evans, Leonard Fitzpatrick, Jane Frost,

Benjamin Green, Bob Hambling, Danielle Hanmer, Roger Jaensch, Kevin Jensen, Rod

Kavanagh, Heather Kay, Bianca Keys, Satoko Kuroda, Russ Lamb, Llynlly Langdon, Kerrie Lock,

Michael Mathieson, Warrick McCorkell, Keith McCosh, David McKitrick, Ross Monks, Lyn

Monteath, Greg Neill, Tida Nou, Hemal Patel, Bruce Penman, Michelle Phung, Amanda

Robertson, Lyn Robinson, Marion Roper, Tim Shields, Geoffrey Smith, Oliver Spohr, Adam

Taylor, Judith Vink, Brenden Ward, Dominic Ward, Jonathon Westacott, Michael Willis, John

Wilmott, and Christine Zupanc.

The Powerful Owl Project is operating in partnership with Birds Queensland, and is proudly

supported by the Queensland Government, including through the Queensland Citizen Science

Grants. The project has previously been supported by the Logan City Council, the Sunshine

Coast Council’s Environment Levy, The Wettenhall Environment Trust, Redland City Council,

Brisbane City Council and the Australian Environment Foundation.

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Executive Summary

When this project started in 2018 the

number of breeding Powerful Owl pairs was

suspected to be around 30 to 50 pairs.

Collation of available data, collection of new

data and modelling now provides certainty

that there are least 70 pairs in the region,

and there is strong evidence to indicate

there are 186 pairs. If we assume that most

records of single owls in remote areas also

likely include a pair, and account for some of

the high densities of owls in some areas

(breeding only 1km apart), we are fairly sure

there are at least 300 pairs. Then using species distribution modelling to predict into the

many areas where there are no data, we get an estimate of 950 pairs in the region. While we

need to confirm that Powerful Owls are found in remote and sometimes higher elevation

areas as predicted by modelling, in three years we have shown that the Powerful Owl

population is six to nearly 20 times higher than suspected initially.

Successful breeding has now been recorded at 46 locations, and 31 breeding hollows have

been detected within 25 territories. A review of breeding success indicates that in the

Brisbane area and the Sydney area breeding success hovers around one fledged chick

produced per breeding attempt. In 2020, that fledging success rate dropped to 0.8 which

could become a concern if repeated in future years. Mortality rates remain unassessed aside

from a handful of reports of vehicle strike or electrocution, but work in New South Wales

indicates mortality rates could be high enough in Australian urban environments to inhibit

population viability in those areas.

These growing understandings would not have been possible without the 548 people

currently formally signed up to conduct field surveys, and the many others who contribute

assistance and data. In 2020 597 sightings were reported during 985 surveys. This marks

another big increase in survey effort. In 2018, 200 Powerful Owl sightings were recorded

from 444 surveys, and in 2019 347 sightings were recorded in 655 surveys. Throughout

Queensland 1,883 sightings have now been collated from 2,223 surveys into Birdata.

Eleven Powerful Owl workshops or presentations were held this year, and workshop content

was also uploaded to YouTube. The project mailing list includes 787 people, 857 people are

signed up to the Brisbane Powerful owl Facebook group, and over 2000 people have

Photo: Powerful Owl chick; Amanda Robertson

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attended various talks. On-line media has reached tens of thousands of people, and broader

media coverage of the project has reached over 1 million people.

Together with QUT, the project has amassed in excess of 10 terabytes of acoustic data. QUT

deployed 16 sensors in active territories to measure detection probabilities and to capture

enough Powerful Owl vocalizations to train automated recognizers. They are also going to

deploy 20 sensors over summer to characterize summer calling, and determine how

detection rates change after the breeding season. Another 44 sensors were deployed in

areas Powerful Owl are known to occur. Data will be analyzed in the coming year, and a

larger deployment is planned for March and April of 2021 with the primary aim of testing and

refining species distribution models. We are optimistic that acoustic monitoring will

transform our ability to detect cryptic species like the Powerful Owl.

While the project has uncovered a lot of good news about Powerful Owl, with a larger

population and reasonable breeding success, the summer bushfires had catastrophic impacts

on many of the forests of eastern Australia. We developed some species distribution models

and overlayed them with fire mapping to discover over 1/3 of three forest owl’s habitat was

impacted by these fires. This prompted a review of the conservation status of these three

owls to determine if the evidence was sufficient for IUCN listing. Unfortunately, data on owl

populations in most of their remote range were not sufficient to demonstrate thresholds for

listing had been clearly met. The review, however, provides an excellent foundation for

future investigations.

Analyses revealed that breeding areas had significantly more forest cover, higher rainfall, and

were at lower elevations than random areas less than 20km away. Breeding plots had a

median of 59% of the plot covered in forest or 187 ha of forest in a 314-ha plot. Random

plots had a median of 21% of the plot covered in forest. While breeding was indicated in

areas with as little as 50ha of forest, those areas also had low density housing with many

trees and / or wide forest corridors to other patches of forest.

We were fortunate in attracting three University of Queensland student placements, Darcy

Brady and Laura Ferris who helped considerably in the field this season. Michelle Phung a UQ

placement from last year submitted the work she led last year on species distribution

modelling to Sunbird. Tyde Bands another UQ student who volunteers on the project also led

a paper submitted to sunbird which reviewed site fidelity, breeding success and occupancy

from the decade long NSW dataset.

This year 41 people responded to our survey about the project and like last year, the results

were highly positive. Encouragingly, the percentage of people who make a record every time

they go out to do a survey, regardless of whether they see an owl, grew from 29% to 49%.

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Feedback also identified a desire for more field training and group outings, as well as few

other places we can look to improve in the coming years.

We are very thankful for the support from the Queensland Government which will allow this

project to continue for two more years.

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Introduction

The Powerful Owl is listed as vulnerable in Queensland but we lack up to date information on

where the owls are found, how big their population is, how that population is trending over

time or what factors are related to breeding success. Powerful Owl are reliant on large

patches of forest with trees from 100 to 500 years old (Kavanagh 1997, Loyn et al. 2001), and

the loss of forest habitat is seen as the primary reason Powerful Owl populations have

declined (Webster et al. 1999, NSW Scientific

Committee 2008). Unfortunately, Powerful Owl can

be especially difficult to detect in Australian forests

(Department of Sustainability and Environment

2011, Cooke et al. 2017), so it is likely that loss of

forest habitat leads to impacts to Powerful Owl that

occur unnoticed. As apex predators, Powerful Owl

also likely perform an important function within

ecosystems (Estes et al. 2011, Wallach et al. 2015),

and due to their large home range it is likely that

many species are conserved when Powerful Owl are

conserved (Senzaki et al. 2015, Burgas et al. 2016,

Senzaki and Yamaura 2016, Yamaura et al. 2018,

Rodríguez-Estrella et al. 2019). Unfortunately, the

threats to Powerful Owl and other wildlife reliant on

forest habitats are increasing (McAlpine et al. 2002)

due to on-going growth of the human population in

Queensland (Queensland Government Statistician’s

Office 2019) and associated on-going forest clearing

(Simmons et al. 2018).

Despite the many good reasons to conserve Powerful Owl as threats to their survival

increase, there is little that can be achieved if the owls cannot be detected (Cooke et al.

2017). Fortunately, it has been shown that engaging large numbers of people in looking for

owls can overcome the difficulties in detection. Sydney’s long-running Powerful Owl

monitoring program has demonstrated that the distribution and breeding success of these

owls can be uncovered with a citizen science program (Bain et al. 2014) . These monitoring

efforts have enabled general and site specific management recommendations to be made

(Kavanagh and Owls 2002, Bain et al. 2014, Lake Macquarie City Council 2014). Powerful Owls

are proving good indicators of the location and condition of some of the best wildlife habitats

in urban areas. As apex predators reliant on the presence of abundant prey (Kavanagh 1988,

Pavey et al. 1994, Cooke et al. 2006), old trees with hollow for nesting, and often large blocks

of mature forest (Bain et al. 2014). A recent study in Victoria successfully modelled the

distribution of Powerful Owl and highlighted the need to establish clear vegetation

Photo: Powerful Owl; Amanda Robertson

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management strategies throughout the urban matrix, an area increasingly being used by

Powerful Owl (Bradsworth et al. 2017). Two-thirds of the habitats in need of protection in

Victoria included areas that are outside existing protected areas (Bradsworth et al. 2017). The

above rich understanding has yet to be developed in Queensland.

Acoustic monitoring also has the potential to overcome the low detection probabilities in

cryptic species like the Powerful Owl. This kind of monitoring is already proving successful for

improving our understanding of other species in Australia (Law et al. 2018). If it works this

kind of sampling could provide more representative sampling of Powerful Owl in remote

areas where citizen scientists are unlikely to travel.

Owl monitoring has been done by Brisbane City Council (Brisbane City Council 2005) and

other owl experts in the region, but there is insufficient data to guide management decisions

that would ensure this species persists in the long-term in Queensland. Monitoring efforts

have occurred at too few sites with too little frequency to determine how owl populations

are changing in this region, let alone why any changes may be occurring. There are also gaps

in our understanding of where breeding owls are found in the region. Further, in order to

develop the best possible management recommendations, we require an understanding of

what habitat factors might relate to the presence of breeding owls, and the ability for any

pair to successfully produce young. Previous studies also indicate that Powerful Owl

populations may be most sensitive to adult mortality (McCarthy et al. 1999). So, a

monitoring program is also needed to capture potential sources of adult mortality, or other

factors that can impact populations aside from habitat loss (Gagné et al. 2015, Eccleston and

Harness 2018, Lohr and Davis 2018). Fortunately, due to the help from many people involved

in this project, we are now on a road to deliver these understandings.

The Powerful Owl project is not just important for conservation of this species and associated

biodiversity (Bennett et al. 2015, Schlagloth et al. 2018), but it can raise environmental

awareness and engage growing numbers of the community in meaningful experiences in the

natural world (Bain et al. 2014). Species like Powerful Owl attract wide public attention and

citizen science projects attract growing

numbers of people to work in the outdoors.

The benefits of connecting to nature are

increasingly being documented for human

health (Keniger et al. 2013, Shanahan et al.

2016), and it is thought that direct experiences

with the natural world are more likely to lead

people toward taking or supporting

conservation actions (Dunn et al. 2006, Zaradic

et al. 2009). We feel broad programs which

educate the community on ecological and

conservation issues are increasingly important as Photo: Powerful Owl chick; Mark Clarke

11

evidence indicates the general public is becoming increasingly detached from the natural

world (Soga and Gaston 2016, Soga et al. 2016). This kind of project serves as a catalyst to

generate broader community interest in the surrounding natural areas.

If google scholar searches provide a crude proxy of how much we have learned about a

species. It looks like we have a lot to learn about Powerful Owl and other nocturnal species,

as a search on Mallard returns 142,000 articles, a search on Powerful Owl returns 1,450

articles, and a search on Marbled Frogmouth returns 162 articles.

In 2017 we undertook a pilot investigation in the Brisbane region to determine project

feasibility, and in 2018 and 2019 we have initiated a wider scale Powerful Owl citizen science

monitoring project in southern Queensland. In 2020 we have partnered with QUT to explore

the utility of acoustic monitoring in helping us refine species distribution models, and

understand correlates of breeding success. This report summarises our progress so far.

Objectives

(Our project is currently focused on Powerful Owl, but there is room for this kind of work on

most nocturnal birds.)

Inspire the general public, and educate

them about nocturnal birds, and their

habitat / conservation requirements.

Train citizen scientists to conduct

surveys to find nocturnal birds and

track breeding success.

Develop/review codes of practice for

such surveys (to protect welfare of

birds): minimum approach distances,

etc.

Survey and monitor the distribution and abundance of nocturnal birds and uncover

why birds are present in some areas and absent in others.

Uncover habitat characteristics, including indices of prey abundance, associated with

species presence and breeding success in nocturnal birds.

Photo: Powerful Owl chick; Jasmine Zeleny

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Develop species distribution and population models of sufficient accuracy to be used

as planning layers by state and council and for assessment of population trajectories.

Identify site-specific management recommendations for nocturnal birds. (Review in

context of various generic codes, e.g. forestry practices, road construction, etc.)

Understand the impact of threats such as vehicle strike, secondary poisoning or

electrocution.

Inform, and support land management for the conservation of nocturnal birds.

Powerful Owl distribution in southeast Queensland

Powerful Owl observations

Before we started the Powerful Owl project in southern Queensland in 2017, we guessed

that there might be 30 to 50 breeding pairs in the region. Since 2017, Powerful Owl have

been recorded in 186 grid cells (5km2 resolution) in southeast Queensland, with additional

sightings recorded from additional 73 grid cells prior to 2017 (Figure 1), many of which came

from the Queensland Government’s historic records (Queensland Herbarium 2020). Two of

these grid cells contains three active

breeding hollows within it, and another

grid cell contains two pairs. Powerful Owl

are also thought to be present in large

blocks of forest that have not been

surveyed. Together, we suggest there are

a minimum of 300 pairs in southeast

Queensland, and initial species

distribution modelling indicates there

could be over 950 pairs in the region (see

abstract below). While there remains a

high level of uncertainty regarding the

population size of Powerful Owl in

southern Queensland, we are confident that

the population is much larger than we guessed

three years ago, possibly nine times higher than originally thought.

Since 2018 we have confirmed 70 Powerful Owl pairs are active in the region, with multiple

sightings of a pair of owls 1 km or less apart. In addition, successful breeding has been

recorded at 46 distinct areas. At 25 of these locations a total of 31 breeding hollows have

now been identified.

Photo: Powerful Owl chick; Amanda Robertson

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The council areas where we were able to identify the most breeding pairs, were those where

targeted funding permitted regular outings where volunteers were taken out into the forest

(Table 1).

Powerful Owls can likely turn up in any forested habitat occasionally (The Department of

Sustainability and Environment 2011), so we want to continue to confirm pairs in locations on

multiple occasions or confirm breeding to get a more precise understanding of population

size.

Throughout Queensland 1,883 sightings have been collated from 2,223 surveys into Birdata.

In 2018, 200 Powerful Owl sightings were recorded from 444 surveys, in 2019 347 sightings

were recorded in 655 surveys, and 597 sightings were reported in 985 Powerful Owl surveys

in 2020.

In 2019, two instances were reported this year where owls flew toward observers landing

within three meters. In both

cases observers left the area

immediately. In 2020 one

observer reported being

swooped by an owl on two

occasions when visiting a

hollow on private property.

The observer subsequently

kept their distance, and were

able to confirm young later in

the year with no further

swooping.

No other swooping or aggressive behaviour has been reported in Queensland Owls. Once

again, this year we did not look for data on mortality, but six Powerful Owl were found dead

due to vehicle collision, one to electrocution, and two others were hospitalised due to

collision.

Table 1. Summary of pairs, breeding pairs and hollows found in council areas of southeast Queensland in 2018 & 2019.

COUNCIL # OF HOLLOWS

# BREEDING PAIRS

# ADDITIONAL

PAIRS

Brisbane 11 18 4

Fraser 0 0 0

Gold Coast 0 1 2

Gympie 0 0 1

Ipswich 1 3 2

Photo: Powerful Owl pair; Amanda Robertson

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Lockyer 0 0 1

Logan 3 7 0

Moreton 1 5 3

Noosa 0 0 0

North Burnett 0 0 0

Redland 6 8 1

Scenic Rim 0 1 3

Somerset 0 0 0

South Burnett 0 0 0

Southern Downs 0 0 1

Sunshine 1 3 0

Toowoomba 1 3 0

Figure 1. Map of Powerful Owl records in southeast Queensland at 25 km2 resolution.

Other Nocturnal bird locations in southeast Queensland in BirdData database

Records on other nocturnal birds have been collected as part of the Powerful Owl project and

there are some historic records in Birdata (Figure 2a – 2e). There is likely more data in other

databases. It has been surprising how few observations of other nocturnal birds are being

recorded during Powerful Owl surveys and this suggests that capturing data on other species

will require more targeted efforts.

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Figure 2a. Map of Barking Owl and Barn Owl records in southeast Queensland at 25 km2

resolution, available in BirdData.

Figure 2b. Map of Southern Boobook Owl and Eastern Grass Owl records in southeast

Queensland at 25 km2 resolution, available in BirdData.

Figure 2c. Map of Masked Owl and Greater Sooty Owl records in southeast Queensland at 25

km2 resolution, available in BirdData.

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Figure 2d. Map of Marbled Frogmouth and Australian Owlet-nightjar records in southeast

Queensland at 25 km2 resolution, available in BirdData.

Figure 2e. Map of Tawny Frogmouth and White-throated Nightjar records in southeast Queensland at 25 km2 resolution, available in BirdData.

Engagement

The project received a large boost in engagement after the Minister for Environment and the

Great Barrier Reef, The Honourable Leeanne Enoch joined us at Mt Coot-tha to announce the

Powerful Owl project would get funding for the next three years as part of the Palaszczuk

Government’s $1.4 million in funding for threatened species projects. This announcement led

to media coverage and growing numbers of people contacting the project with sightings or to

get involved.

Since then, BirdLife, Birds Queensland, Natura Pacific and other groups and local councils

have helped the project reach a growing number of people. The restrictions around activities

due to COVID-19 also resulted in a large increase in opportunistic sightings and on-line

engagement. Details on the numbers of people participating in the project, public

engagement

17

Number of people involved

The project mailing list includes over 787 people, 857 people are signed up to the

Brisbane Powerful Owl Facebook group, and over 2,000 people have attended various

talks since 2018.

548 people are now formally signed up to the project (148 from 2020) and have

attended workshops were given maps of areas, permits, notification requirements,

methods, and flyers for letterboxing private landholders.

11 Powerful Owl presentations were given this year attended by 420 people. Six

included the full three-hour workshop followed by a field visit, two included a 1-hour

presentation followed by field visits, one was an on-line live workshop, and two one-

hour presentations were given (see below for details).

COVID-19 forced the cancellation of four workshops, but all those who had RSVPed

were sent links to on-line videos of workshop content (see below).

Groups of volunteers are starting to form in some areas with local leaders.

Over 300 volunteers have gone out in the field with me or other experienced people

to actively look for owls or check on existing territories on casual visits outside those

at workshops.

We trialled the collection of data on the number of arboreal mammals observed, and

the distance walked on each survey in a google form. While 7 people did report these

data indicating and average of 4.2 arboreal mammals were seen on walks of an

average of two kilometres. These variables will need to be incorporated into Birdata if

we hope to capture enough data to analyse. We also talked about including the

number of trees with large hollows as another variable to include in the future.

Photo: Powerful Owls with different prey items; Amanda Robertson

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Table 2. Summary of Powerful Owl workshops and presentations held in the last year.

Date Location URL # of people attended

Full three-hour workshops followed by field visit

29/02/2020 THECA, 47 Fleming Rd, Chapel Hill

https://tinyurl.com/rrt45sm 52

1/03/2020 Toowoomba City Library, 155 Herries Street, Multipurpose Room, Level 3, Toowoomba City

https://tinyurl.com/rn9uneg 24

7/03/2020 177 Meakin Rd, Slacks Creek https://tinyurl.com/rv4nq9m 24

8/03/2020 Ipswich Central Library, 40 South St, Ipswich, Qld

https://tinyurl.com/vp3232c 22

14/03/2020 Indigiscapes, 17 Runnymede Road, Capalaba

https://tinyurl.com/smyhcbj 55

15/03/2020 149 Acacia Rd, Karawatha https://tinyurl.com/wnydhg8 31

One-hour presentation with no field visit

26/8/2020 Gecko Environment Council- Currumbin RSL, 165 Duringan St, Currumbin

https://tinyurl.com/y3fuo2vv 82

22/10/2020 Albert Valley Wilderness Society, 1368 Beenleigh Rd, Cedar Creek

https://tinyurl.com/y5f7njhz 35

One-hour presentation followed by field walk

21/9/2020 Woodfordia's Bushtime, 87 Woodrow Rd, Woodford

https://tinyurl.com/y49vcew2 20

28/9/2020 Woodfordia's Bushtime, 87 Woodrow Rd, Woodford

https://tinyurl.com/y49vcew2 25

On-line live workshop one-hour

25/9/2020 On-line Gold Coast workshop, live, Natura Pacific and City of Gold Coast hosted

https://tinyurl.com/y4m2grfz 50

Table 3. The links to on-line workshop content and number of views so far

Name of video URL Number of views

The Powerful Owl Project - Overview https://youtu.be/ieDWU78HuCc 618

Overview from Gold Coast on-line workshop

https://tinyurl.com/y4m2grfz unknown

The Powerful Owl Project – South East Queensland Owls and Ecology

https://tinyurl.com/y4r8nb3s 857

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The Powerful Owl Project - Research https://youtu.be/A5Nxm-8EGJI 155

The Powerful Owl Project - What we have learned

https://youtu.be/eoRfC2ykcSU 255

The Powerful Owl Project - How to find Powerful Owls

https://youtu.be/1kqU1AY8-0w 613

The Powerful Owl Project - Project Safety and Rules

https://youtu.be/5NBRxruVUv8

129

The Powerful Owl Project - QUT Acoustic Monitoring

https://youtu.be/-gOK_sv80uI 286

The Powerful Owl Project - Glider Talk https://youtu.be/9NtRRm4P9pI 175

Photos: Eleven Powerful Owl presentations or workshops were given in 2020, with

attendance at each workshop varying from 20 to 55.

20

Volunteer engagement and feedback

Promotion of the project was helped again this year

with the help of BirdLife, Birds Queensland, and

Natura Pacific. We were also invited to speak to the

members of The Hut Environmental & Community

Association (THECA), Gecko Environment Council,

Woodfordia, and the Albert Valley Wilderness Society.

Further promotion was provided by council staff,

through word of mouth, email announcements,

newsletters, social media, and advertising.

Advertising was purchased again this year in the online

events bulletin Weekend Notes, and through boosting

on Facebook. With a $75 Weekend Notes

advertisement, 213 unique readers were reached

with an announcement of a Powerful Owl workshop

schedule. A $345 spend on Facebook reached far more people (49,271), with 4,062

engagements and 4,277 clicking on links in those posts about the workshops. In 2020 we also

saw a very large increase in the number of people visiting the Powerful Owl website

https://birdlife.org.au/projects/urban-birds/powerful-owl-project-pow with 23 times more

unique visitors visiting the site in 2020 than did in 2019, and 41 times more people

downloading content from the site. A variety of Powerful Owl Facebook posts have now

exceeded tens of thousands of likes and shares. The Project’s private Facebook group has

now grown to 857 https://www.facebook.com/groups/brisbane.powerful.owls/

Additional promotion resulted from media coverage (see below). Owl experts Jasmine Zeleny

and Matt Wright have volunteered to help with field work and helped deliver half the content

of the workshops.

The project has continued to grow this year, with 148 formally signing up to participate. The

most growth this year has been in informal participation, and a growing number of

opportunistic sightings being reported.

We again asked volunteers to fill out a survey about their participation in the Powerful Owl

project. A few new questions were added this year, while many were left the same to

provide some comparison. Last year 58 people responded, and this year 41 people

responded to the survey. It is hard to know how representative these results are of the

entire 548 people signed up formally to the project, but results are still informative.

This year participants did an average of 16 surveys (range 0 to 70) in 2020, which is slightly up

on the average of 11 last year. Participants also walked on average of 2.6 km per survey

(range 0 to 7), which is down slightly on last year’s average of over 3km. Participants this

Photo: Powerful Owl; Michael Willis

21

year indicated they drove on average 18km to do surveys (range 0 to 200). 82% of

participants ranked the project at 8, 9, or 10, with 42% giving it a perfect score of ten. These

results were very similar to last year with no one scoring the project less than five, but there

were far more people who scored the project a ten this year. 88% of participants this year

would recommend the project to a friend, which is down slightly on the 93% reported last

year.

This year 90% of respondents learnt something new about owls (96% last year) and 78% now

find themselves looking and listening for owls when they get the chance (86% last year). In

addition, 73% of them felt proud to be a part of the project and the work they were doing

(76% last year), while 61% reported the project was allowing them to reconnect with nature

(50% last year). 32% of participants met new people in their area that they go out on surveys

(30% last year) with and 63% of people engaging with others about the project (15% last

year). These results indicate that most people found the project rewarding and engaging,

with over half reporting the project was a catalyst to

reconnecting with the natural world. The project also

required increases in physical activity with volunteers

reporting on average walking over two kilometres on

each survey while conducting on average 16 surveys

for a total average of 41 kilometres walked by each

volunteer.

We were encouraged to see that an increasing

proportion of people are submitting records each time

they go out to look for owls, even if they do not see

anything (Figure 3). In 2019 29% of participants

indicated they always entered their surveys in Birdata

and that increased to 49% in 2020. This encouraging

result indicates that we will have much improved data

on sampling effort, which will allow us to develop more precise predictions of species

occupancy.

A few additional questions were added to the survey this year. One was if people wanted to

shorten the workshops. 52% indicated they did not want a change while 41% wanted to

“shorten the indoor presentation, and cover field identification, calls and survey protocols on

a field trip.” Fortunately, we can accommodate both going forward. We asked participants

to rate the workshops and 67% indicated they were excellent, 31% indicated they were good,

and the remaining 2% indicated they were fair. Also 95% of people were accessing a variety

of on-line resources with 71% accessing owl calls, and nearly half watching on-line videos

accessing last year’s report and survey methodologies. 60% have used the maps provided on

survey locations and over 30% of people accessed other material in a shared Dropbox folder,

Photo: Powerful Owl; Kevin Jensen

22

downloaded management guidelines, downloaded the project flyers for letterboxing, and 6%

have downloaded the education materials.

Figure 3. Results of volunteer survey regarding the frequency that participants record their

surveys in Birdata regardless of whether they see an owl 2020 (n = 41), and 2019 (N=59).

Participants also provided written feedback (Appendix A) which we will draw on to look to

improve the program next year. The comments were varied, but many indicated a desire for

more field training, and chances to get together. Program improvements will also be looked

at during the end of year meeting and our project advisory committee meeting in early

December.

To further help people to learn about nocturnal birds, thousands of nocturnal bird booklets

have been printed with funding from ABEF and Ipswich City Council. These are distributed at

all live presentations and are also available on-line:

https://birdlife.org.au/documents/Nocturnal_birds_reduced.pdf Grant funding from ABEF

also allowed us to purchase blue-tooth speakers and red torches for some of the most active

volunteers.

23

Flyers for letterbox drops were also printed this year and given to some volunteers who

distributed them with some responses that led to a couple more Powerful Owls being

located.

Education materials have in previous years been developed by the Powerful Owl project in

NSW to fit in with the curriculum. See the Powerful Owl education kit available for download

here: http://birdlife.org.au/projects/powerful-owl-project We will continue to look for

people that might be interested in delivering education programs in schools.

Electronic monthly newsletters are sent to the 787 people on the project monthly email list

and links to each newsletter are posted to Facebook.

October 2020: https://tinyurl.com/y3kntm7w

September 2020: https://tinyurl.com/y2f7r867

August 2020: https://tinyurl.com/y33enc4d

July 2020: https://tinyurl.com/y3qjy878

June 2020: https://tinyurl.com/y4763b9x

May 2020: https://tinyurl.com/y3oqfdvo

April 2020: https://tinyurl.com/yyunnyqx

March 2020: https://tinyurl.com/y4deojq4

February 2020 update 2: https://tinyurl.com/y3lorqob

February 2020: https://tinyurl.com/y5qcx7rr

December 2019: https://tinyurl.com/y4d6xxa7

November 2019: https://tinyurl.com/yxg2newh

Rat Poison Campaign

BirdLife made a submission and initiated a campaign to regulate second generation anti-

coagulant rodenticides. The Powerful Owl project staff and volunteers assisted with these

submissions. These compounds are highly regulated in the EU, the USA and Canada. Almost

4,000 people made a submission to the Australian Pesticide and Veterinary Medicines

Authority (APVMA) review into rodenticides through the BirdLife network, asking for the most

harmful second-generation products to be taken off supermarket shelves.

The APVMA has recently released a first response to those review submissions, indicating they

will be updating labelling of products. While this is a positive move it does not go nearly far

enough to protect birds, or to bring Australian regulations in line with European and North

American standards. BirdLife will continue to push for stronger regulation of these compounds.

https://www.actforbirds.org/ratpoison

Photo: Powerful Owl; Sylvia Alexander

24

Media attention

As we near the end of 2020 we estimate that media coverage has reached over 1 million

people throughout southeast Queensland with stories about both Powerful Owl and the

project (Table 4). In 2019, the greatest amount of media coverage came as a result of the

minister for the environment announcing three years of project funding. In 2018, media

attention came as a result of parallel interest in a zip-line development at Mt Coot-tha, and a

press release sent out by one of our volunteers. In both years we have generated numerous

internal project updates, and external newsletter articles and social media links.

Table 4. Summary of media coverage

Year Outlet / program location reach URL

2020 ABC Radio: Catherine Feeney

Southeast Queensland

Tens of thousands

https://tinyurl.com/y3vug8np

2020 ABC Radio: Scenic Rim Local


Thousands NA

2020 ABC Print: News Science

National Hundreds of thousands

https://tinyurl.com/y8ofrz8p

2020 Channel Ten TV: Totally Wild- featuring Jasmine Zeleny and Rob Clemens


https://tinyurl.com/y3jkqgpr

2020 Sydney Morning Herald


https://tinyurl.com/y5wutnyg

2020 Podcast: Natura Pacific

National Tens of thousands

https://tinyurl.com/y545sg4a

2020 Cosmos magazine National Thousands https://tinyurl.com/yycnv4q7

2020 Planet Ark article National Thousands https://tinyurl.com/yym97tme

2020 Print: The Local Bulletin Brisbane West – by Jim Butler

Local SE Queensland

Thousands https://tinyurl.com/y5uaekfa

2020 Electronic BirdLife communications

Tens of thousands

https://tinyurl.com/y26qt68r https://tinyurl.com/y6ctum32 https://tinyurl.com/yyzf664m https://tinyurl.com/yxnbm9at

2019 ABC – on-line National Hundreds of thousands

https://tinyurl.com/y2e7j87f

2019 Channel 7 TV: 7pm news


Hundreds of thousands

https://tinyurl.com/yybxjvax

25

2019 Gold Coast Channel 7 Facebook


Tens of thousands

https://tinyurl.com/qmwepxv

2019 Queensland Government Facebook - Science


Thousands https://tinyurl.com/wc5jpcd

2018 Print: Brisbane Times


https://tinyurl.com/y7dtppa6

2018 Print: Sydney Morning Herald


https://tinyurl.com/y64m3tau

2018 Print: Beaudesert Times

Local southeast Queensland

Thousands https://tinyurl.com/y6slbna5

2018 Natura Pacific: on-line doco

National Tens of thousands

https://tinyurl.com/yypowetb

2018 Print: Jimboomba Times


Thousands https://tinyurl.com/y6n5hpdf

2018 Print: Redland City Bulletin


Thousands https://tinyurl.com/y5yl766q

2018 ABC TV Southeast Queensland

Hundreds of thousands

https://tinyurl.com/y7f4e89z

2018 Print: Architecture.com

National Thousands https://tinyurl.com/y6efd57c

2018 Print / on-line: Land for Wildlife article


Thousands https://tinyurl.com/yxor59of

Stakeholder Engagement

Many council and state employees are included on project

email updates, and are sent data and project reports at the

end of the season. Last year we had our first meeting of the

Powerful Owl advisory group, which included

representatives from within the project as well as QUT,

Deakin University, University of Queensland, Redland City

Council, Moreton Regional Council, Ipswich City Council,

Sunshine City Council, Faunagraphic, and BirdLife national

office.

We will be having another meeting of the project

advisory committee in early December of this year. Photo: Powerful Owl; Nick Bradsworth

26

So far, the diverse group of attendees advised on ways to improve the project, discussed

ways improve conservation instruments within different levels of government, and to

identified related projects of interest to participants.

Acoustic Monitoring

QUT Acoustic Monitoring

The aim of this research project is to use bioacoustics to monitor Powerful Owls (Ninox

strenua) in south-east Queensland. The development of an automated species recognition

tool will provide insight into the vocalisation habits of this secretive species, with the aim of

providing an efficient method for monitoring breeding success and improved field detection

relative to traditional observation methods. Acoustic recognisers are automated tools

developed to detect vocalisations of a particular species amongst complex environmental

acoustic data (Duan et al., 2011). One of the most promising applications of passive acoustic

monitoring using ARUs is the monitoring of vocal cryptic species, such as the Powerful Owl

(Duchac et al., 2020).

This project addresses the following questions:

• What are the vocalisation characteristics of Powerful Owls and can different

vocalisations be linked to behavioural functions?

• How does the vocalisation behaviour of Powerful Owls change throughout the

breeding season?

• Can automated acoustic recognisers be utilised to determine whether a pair of

Powerful Owls have bred successfully?

• How far do Powerful Owl vocalisations travel in different environments? How should

acoustic monitors be placed in order to maximise monitoring efficiency?

Current Progress:

16 acoustic monitors were

deployed for approximately 6

months in active owl territories and

have now been returned from the

field (Figure 4,). Approximately 7

terabytes of long-duration

recordings have been obtained.

Manual annotation of the

recordings is being conducted in

Raven Pro in order to build a Figure 4. Locations of initial acoustic sensor deployment

locations

27

training dataset for acoustic recogniser application. Directional recordings will be obtained

over the following months for call classification. Once manual annotation is completed,

recogniser testing will begin, along with call attenuation testing. 20 Birdlife Audiomoths

(small acoustic monitoring devices) will also be deployed in the coming weeks to provide

additional testing data and gain insight into summer vocalisation habits.

Additional deployments

Seventy-seven acoustic sensors are being deployed in 2020 (Figure 5). These deployments

are intended to further test how often Powerful Owl are detected when they are deployed in

areas where Powerful Owl have been detected previously. We were also hoping some of

these deployments might confirm the presence of a territorial pair, or uncover evidence of

breeding success in areas where it was not detected in 2020. Data has been retrieved from

44 locations, and five additional sensors are currently in the field. Unfortunately, seven

sensors were stolen, and one sensor was left on the ground but the mounting strap and

micro SD card was stolen. Twenty additional sensors will be deployed in November by QUT in

order to explore how well acoustic monitoring can detect breeding success in territories

where young owls were produced this year. There is little understanding of how often

Powerful Owl call over summer, or how well breeding success might be detected once the

chicks are flying around well. Close to 3TB of acoustic data has been collected and a few

more TB are expected to be collected by the year’s end. These data will be analysed, and

screened for Powerful Owl detections in the coming year.

Deployments at 30 known breeding locations are planned again in March and April of 2021 to

test the detection probability at sites known to have Powerful Owl at a time of year when

adult birds are calling the most throughout the area to set up a territory prior to breeding. In

March and April, to test and refine species distribution models, another 60 sensors will be

deployed. Thirty will be deployed at locations predicted to have suitable habitat and where

Powerful Owl have not been recorded previously. A third set of 30 sensors will be deployed

in forested areas with at least one tree of at least 85cm diameter at breast height which are

predicted to be unsuitable for Powerful Owl.

28

Figure 5. Locations of 77 acoustic sensor deployment locations in 2020. Red dots are

locations where seven sensors were stolen.

29

Impact of summer 2019/20 bushfires on forest owl habitat

The fires in eastern Australia during the summer of 2019/20 were unprecedented in scale

and severity. Remote sensing data on fire extent were overlayed onto species distribution

models to estimate the impact these fires had on the habitat of Powerful Owl, Australian

Greater Sooty Owl, and Southern Masked Owl.

Methods

Bird records were sourced from Birdata

(BirdLife Australia 2020) and ebird (Sullivan

et al. 2009) and included all records of each

owl in Australia. The records from these

sources included Powerful Owl 19,462

records, 3,721 Australian Greater Sooty

Owl records, and 5,402 Southern Masked

Owl records.

The environmental predictor variables that

were selected were believed to be related

to the ecological niche of these owls and

included: area of closed forest, area of

woodland forest, area of open woodland

forest, area of rainforest, average normalised

difference vegetation index (NDVI), average

vegetation forest height, area of remnant vegetation cover, stream density, stream aspect,

annual precipitation, maximum temperature, precipitation in the wettest quarter and

temperature in the coldest quarter, and population density. All variables were either totalled

or averaged at a 4km2 resolution (Table 5). The 4km2 resolution was set to capture variables

at the scale of core breeding habitats and to minimise overlapping territories which are

occasionally only one kilometre apart.

Variables were aggregated, processed and resampled to a matching resolution and projection

using ArcMap (v.10.7.1, ESRI, Redlands, CA, USA) and in RStudio (RStudio Team 2015, R Core

Team 2018) using the following packages: ‘raster’ (Hijmans 2017), ‘rdgal’ (Bivand et al.

2018), ‘sf ‘(Pebesma 2018), ‘sp’ (Pebesma and Rivand 2005) and ‘dplyr’ (Wickham et al.

2019).

Fire data were derived from VIIRS sensor aboard the joint NASA/NOAA Suomi National Polar-

orbiting Partnership (Suomi NPP) and NOAA-20 satellites at a resolution of 375m. NRT VIIRS

375 m Active Fire product VJ114IMGTDL_NRT is available on-line

https://earthdata.nasa.gov/firms doi: 10.5067/FIRMS/VIIRS/VJ114IMGT_NRT.002

Photo: Powerful Owl; Brett Coleman

30

Spatial variation in sampling effort was accounted for by generating a spatial bias grid layer

for use in Maxent which contained the number of Birdata or eBird surveys conducted in each

grid cell.

Table 5. Predictor variables used in Maxent models generated for three forest owls in Australia.

Predictor Description Reference

Area of four classes of forest cover

Classified forest cover at 100m2 resolution was reclassified into four forest classes: closed forest, woodland, open woodland, and rainforest. The area was totalled in each 4km2 grid cell for each of these four classes.

Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES, 2019)

Normalised difference vegetation index (NDVI)

Averaged over two years (2018 and 2019), based on four six-month periods of NDVI data and averaged by resampling from 100m2 resolution.

Bureau of Meteorology (BOM, 2019)

Vegetation height Vegetation height was totalled from 100m2 resolution data.

Terrestrial Ecosystem Research Network (TERN, 2011)

Climatic variables Averaged from 1976 through 2005 and resampled from 5km2 resolution. Climatic variables included: annual precipitation, maximum temperature, precipitation in the wettest quarter and temperature in the coldest quarter.

Future climate layers for Australia (Vanderwal, 2012).

Remnant vegetation The area of remnant vegetation was first converted from polygons to a 100m2 raster, and then area was totalled.

(Queensland Government, 2018)

Stream density and stream aspect

The total length of streams in each 4km2 grid cell was used to represent stream density, and the stream aspect was derived from averaging reclassified aspect into four 90-degree directions with southern aspects given a value of 1, east and west a value of 2 and north a value of 3.

(GeoScience Australia, 2019)

Population Density The density of human population at 100m2 resolution was totalled within each 4km2 grid cell.

Australian Bureau of Statistics (ABS, 2017)

Models were run iteratively in MaxEnt machine learning software which has proven to

predict distributions well from presence only data (Phillips et al. 2004, Phillips et al. 2006,

Elith et al. 2011). The following settings were used within Maxent: output format was

‘cloglog’, predictor response curves and jackknife tests were included, all hinge features were

selected, a random seed value was used with five replicates of 5,000 iterations using cross-

validation, and samples were added to the background with the regularization multiplier set

to a factor of one. Model performance was assessed using the area under the Receiver

Operating Characteristic curve (AUC) (Elith et al. 2011). The predictions were mapped as

probabilities of occurrence and as either suitable or non-suitable based on a threshold rule to

31

maximise training sensitivity plus specificity. That number of cells was then divided by four to

come up with an estimate of the number of pairs likely to be found in the study area. This

step assumed there would be one pair per 16km2 which is close to the average Powerful Owl

home range of 14.6 km2 (Bradsworth et al. 2017).

Results

Maxent model AUC suggested these models did a fair to good job of capturing the

distribution of Powerful Owl, Australian Greater Sooty Owl and Southern Masked Owl with

values of 0.85, 0.93 and 0.90 respectively. When overlayed with estimates of the areas

burned in the 2019/20 summer bushfires of eastern Australia over 1/3 of the predicted

habitat for each of these species was impacted by fire with 31.5% impacted for Powerful Owl,

40.3% impacted for Australian Greater Sooty Owl, and 32.2 % impacted for Southern Masked

Owl. These values are broadly similar if somewhat higher than estimates from independent

work conducted elsewhere (see Table 6 below). The recently published work (Ward et al.

2020) used more precise fire mapping data which may account for some of these differences.

Also, we used some predictive variables such as forest cover which may have resulted in

more precise predictions for these species as opposed to the bio-climatic variables used in

Ward’s work. Either way, the results are broadly similar and raise concerns about the possible

impacts of possible more frequent or severe fire on these owls in future decades.

Figure 6. Species distribution models generated with MaxEnt software for Powerful Owl, and

overlayed with estimated fire mapping from the summer of 2019/20 derived from

NASA/NOAA VIIRS sensor data. Top shows probability of occurrence and bottom shows

suitable habitat based on threshold values that maximized training sensitivity plus specificity.

32

Figure 7. Estimates of suitable habitat impacted by fire: Powerful Owl 31.5%, Australian

Greater Sooty Owl 40.3%, and Southern Masked Owl 32.2%. Suitable habitat was estimated

by maximizing training sensitivity plus specificity of Maxent derived predictions. AUC values

were 0.85, 0.93 and 0.90 respectively.

33

Two research papers submitted to Sunbird in 2020

Michelle Phung, and Tyde Bands, two students at UQ each led a paper which was submitted

for review to the journal Sunbird. If accepted for publications the full papers will be freely

available on-line https://birdsqueensland.org.au/sunbird_downloads2.php

Michelle has led a paper on her species distribution modelling which she presented in last

year’s annual report, and Tyde has presented a review of nest site fidelity, breeding success

and occupancy rates of Powerful Owl based on New South Wales data.

Abstracts of both papers are presented below.

Phung, M., Clemens, R. S. (2020) How many Powerful Owl Ninox strenua are in South East

Queensland? In Review Sunbird.

ABSTRACT

The Powerful Owl (Ninox strenua) is a threatened cryptic apex predator with a poorly

understood distribution in southeast Queensland (SEQ). A citizen science project was initiated

in 2018 to overcome low detection probabilities and grow knowledge of the distribution of

Powerful Owl in (SEQ). Predicting where Powerful Owl occur in the landscape is of growing

importance due to ongoing clearing of forest habitat in SEQ. In this research, we produced a

species distribution model (SDM) using MaxEnt to improve our understanding of the number

of Powerful Owl in SEQ, to help us improve where we target survey effort, and to determine

how much additional work will be required to develop accurate, high resolution mapping

suitable for use in planning layers. Recently collected data, historic data and ecologically

relevant environmental predictors were used to generate this SDM. The model was refined

iteratively to account for spatial sampling bias. The predictions generated from the best model

indicated that Powerful Owl habitat is widely distributed throughout SEQ and suggests that

Powerful Owls are more abundant than previously thought. Available observation data suggest

there could be 350 pairs, while SDM estimates indicate there could be over 950 pairs in SEQ.

More work is needed to verify these estimates, and to develop models of sufficient accuracy

to be incorporated in planning schemes. These improvements will require better predictor

variables, more representative sampling, and additional measures to address sampling bias.

34

Bands, T. L., Mott, B., Zeleny, J., Wright, M., Clemens, R. S. (2020) Nest site fidelity, breeding

success, and occupancy of Powerful Owl Ninox strenua as indicated from a long-term citizen

science project in New South Wales. In Review Sunbird.

ABSTRACT

Birdlife Australia’s Powerful Owl Project has amassed a dataset on Powerful Owl (Ninox

strenua) territory occupancy and breeding success that spans 12 years and is inclusive of 228

separate territories in the greater Sydney region of New South Wales. Year-on-year Powerful

Owl nest site fidelity averages 76%, with a recruitment rate of 1.02 fledglings per territorial

pair. On average, breeding is attempted in 59% of occupied territories each year, and an

average of 92% of territories are occupied in any given year. Over four years, 46% of pairs

switched nest trees at least once. Statistical tests did not reveal any difference in the number

of chicks produced if pairs switched nest trees or re-used nest trees to which they had fidelity.

No relationships were found between average breeding success in a territory and human

population density nor distance to nearest neighbouring Powerful Owl nest tree. Recruitment

rates suggest stable recruitment in this largely suburban population of Powerful Owl. The

switching of nesting trees by Powerful Owl reinforces the importance of having large trees with

hollows in the landscape. Long-term Powerful Owl recruitment will likely require multiple

potential nesting trees, as well as hollows for their preferred arboreal prey.

35

Review of conservation status of three forest owls The summer bushfires of 2019/2020 prompted a review of the conservation status of three

forest owls of eastern Australia including the Powerful Owl, the Greater Sooty Owl, and the

Southern Masked Owl. At this time data was found to be insufficient to warrant listing under

IUCN criteria, but we report the findings of the review below.

Further work to confirm the population impacts of the

recent fires, to quantify population declines, or which

demonstrate the impact of high mortality rates or

poor breeding rates on population viability will be

required to demonstrate that thresholds for IUCN

listing have been met.

Data were not sufficient to capture population change

throughout most of the range of these three forest

owls. When records were excluded if within 50km of

Melbourne Sydney or Brisbane, there were few

records left to assess population change throughout

most of these species’ ranges (mean # of records each

year in remote areas: Powerful Owl = 72; Greater

Sooty Owl = 18; Southern Masked Owl = 20).

The criteria for listing species as threatened have

become more stringent in recent years. For species

that are declining, thresholds need to be exceeded in

a time period spanning over three generations. For

these owls the time periods are 24 years for Powerful

Owl, 17 years for Australian Greater Sooty Owl, and 12 years for Southern Masked Owl.

Under IUCN, criterion A thresholds for a vulnerable or near threatened listing would be the

most likely to be met. However, evidence would need to indicate that the population had

declined by 30% for a vulnerable listing to be given or by 25% for a near threatened listing.

While the threats highlighted below lead us to suspect that these thresholds may have been

exceeded, we do not have sufficient data to demonstrate these declines have happened.

Population declines are inferred due to ongoing loss of large hollow-bearing trees, forest

clearing, and recent extensive bush fires. Global warming is expected to increase the

likelihood of both fire and drought throughout the range of these species. Overall forest

habitat and large trees with hollows are predicted to continue to be lost.

Further, while these thresholds were exceeded when looking at the amount of habitat

impacted by fires in 2019/20, fire severity was not believed to have been severe enough in all

these areas to have resulted in over 25% of these populations to have been killed in the fires

Photo: Australian Greater Sooty Owl;

Amanda Robertson

36

(Table 6). This was based on assumptions made about four classes of fire severity impacted

populations, with 10%, 30%, 80% and 100% of each population assumed to have been killed

in the four classes of fire severity.

None of these species would currently meet criterion B or D. Currently, only the Australian

Greater Sooty Owl has a population of less than 10,000 mature individuals in the population

which is one of the thresholds for Criterion C. However, Criterion C also requires thresholds

of 30% or 25% decline are clearly demonstrated with data. Criterion E requires a population

viability analysis, which has not been conducted for any of these species. It has been noted

that Powerful Owl in urban areas have high mortality rates, and are known to occupy

territories where they cannot breed, but no data on mortality or recruitment is available from

most of any of these species ranges.

Table 6. Estimates of fire impacts and population decline are reported here.

Species % habitat burned 1

% habitat burned 2

% habitat burned 3

% killed 2 mean and range

Rate of annual population decline 4

p-value of population decline 4

Powerful Owl

31.5 17.7 23 10.6 (7.4 – 14.9)

-0.002 0.89

Greater Sooty Owl

40.3 32.5 38 19.6 (13.6 – 27.4)

-0.2 0.64

Southern Masked Owl

32.2 20.1 NA 12.0 (7.4 – 14.9)

-0.014 0.711

1 Estimate taken from this document 2 Estimates reported from separate internal assessment by BirdLife Australia 3 Estimate reported from published paper (Ward et al. 2020). 4 Estimates based on reporting rates from data > 100km from cities (few records)

37

Powerful Owl Ninox Strenua

The following people helped compile the information in the review below: Larry Chen,

Robert Clemens, Nick Bradsworth, Holly Parsons, Beth Mott, and Raylene Cooke.

Overview

The Powerful Owl is currently listed as Vulnerable in Queensland, Vulnerable in New South

Wales, and Threatened in Victoria. It is not listed under the EPBC Act, no recovery plan or

federal conservation advice has been drafted. IUCN status is currently at Least Concern and

our review did not uncover sufficient data to change that listing. Combined threats are

suspected to have impacted these species enough for listing, but evidence is lacking.

Table 7. Summary of Powerful Owl population

Metric Estimate Minimum Maximum Reliability Source

Extent of occurrence

396,000 km2 376,000 km2 415,800 km2 High This document

Area of Occupancy

195,000 km2 NA NA Medium BirdLife 2020

Number of mature individuals

13,000 7,000 19,000 High This document, Garnett & Crowley 2000

Generation Time

8.2 6.2 10.3 Low Bird et al. (2020)

Infraspecific taxa

Monotypic.

Taxonomic uniqueness: high (Hogan 2008); subspecies/species: 1, species/genus: 37,

genera/family: 28, families/order: 2.

Range

The Powerful Owl is endemic to eastern and southeastern Australia, where it is found mainly

on the seaward side of the Great Dividing Range (HANZAB 2006). Most widespread in New

South Wales, where approximately half of the population is estimated to occur (NSW

Scientific Committee 2008). In Queensland, found only in the southeast, principally south of

the Dawson River (Pavey 1993; HANZAB 2006). Limited to southeast in Victoria, and

presumed vagrant in Southern Australia (HANZAB 2006).

Abundance

The number of mature individuals is suspected to be at around 13,000 based on MaxEnt

predicted area of occurrence divided by a suspected average home range / density (Clemens

2020). Ongoing population decline is inferred from forest clearing (Evans 2016; DEC, NSW

38

2006; Bruce et al. 2020), and widespread bushfires in the summer of 2019-20. Recent

modelling indicated that 31% of this species’ predicted area of occurrence was impacted by

these bushfires. Threats across this owl’s range are likely leading to a significant loss of

habitat.

The global population of mature individuals has been estimated to be at approximately 7000

individuals (Garnett and Crowley 2000), with 3000-4250 individuals in the core of its range

and 2000-3250 in New South Wales (Garnett & Crowley 2000). Another estimate places the

population in New South Wales at 2000 pairs, with a minimum of 10,000 individuals (Debus

1994; Kavanah 1997). In greater Melbourne, there are estimates of around 30 pairs (Cooke

2020). In urban Sydney the known number of territories has expanded from 50 to over 230

territories since 2011. Whilst some of this population increase can be attributed to greater

monitoring effort, historical indigenous records from the area do not identify the regular

presence of Powerful Owls in the 1940s and earlier, suggesting the urban population increase

is a recent phenomenon (B. Mott, pers. comm. BirdLife July 2020). In Greater Melbourne,

there are estimates of around 30 pairs (N. Bradsworth, pers. comm. Deakin University July

2020).

While the species has shown adaptive ability in utilising degraded and anthropogenic habitats

such as city parks (Isacc et al. 2014), deforestation through logging and bushfires have caused

an ongoing decline in its population (HANZAB 2006; Department of Environment and

Conservation (NSW) 2006; NSW Scientific Committee 2008).

Ecology

Powerful Owls inhabit sclerophyll forests and woodlands, as well as forest edges, plantations

and extensive parklands (Isaac et al. 2008, Olsen et al. 2020). This species frequently favors

dense, well-shaded areas of structurally diverse forest, especially close to gullies or streams,

for roosting (Cooke et al. 2002, Olsen et al. 2020). Eggs are laid in the winter, from May to

June (NANZAB 2006), in the large tree cavities averaging 1 meter wide and 2 meters deep

(NSW Scientific Committee 2008; Cooke 2000). Owls typically select older living trees of

advanced age; breeding pairs in Victoria selected trees between 350 and 500+ years of age

(HANZAB 2006). Diet consists of significant numbers of medium-sized to large mammals,

particularly arboreal species, including Common Ringtail Possums and Greater Gliders

(HANZAB 2006; Cooke & Wallis 2004; Cooke et al. 2006). Powerful Owls predate primarily

arboreal and occasionally terrestrial mammals, as well as bats, birds, and invertebrates

(HANZAB 2006). In Sydney there are several pairs eating mostly rats and rabbits (B. Mott,

pers. comm. BirdLife July 2020). Home range size estimates are extremely varied and are

likely linked to prey availability, from over 4700 ha in box-ironbark forests (Soderquist and

Gibbons 2007) to as small as 338 ha in suburban Melbourne (Bradsworth et al. 2017).

Movement patterns within their home range is heavily dependent on the amount of riparian

vegetation available, with areas of concentrated movement and hunting close to river

systems (Cater et al. 2019).

39

Monitoring

A variety of monitoring has been undertaken at local scales over the years (HANZAB 2006). In

Victoria, research and monitoring of the urban Melbourne population has continued for over

25 years at Deakin University (Cooke et al. 2018). In the broader Sydney region, BirdLife has

run a monitoring program (Bain et al. 2014), which has expanded to Melbourne and Brisbane

in recent years. Generally, there is only opportunistic monitoring throughout most of the

Powerful Owl’s range (e.g. Bilney 2013).

Threats

Trends of deforestation for purposes such as timber, ranching, and settlement expansion

have resulted in loss of habitat for this species (NSW Scientific Committee 2008; Isaac et al.

2013; Cooke et al. 2017). In all, 53% of Powerful Owl forest habitat is estimated to have been

lost (Simmonds et al. 2019). Additionally, the loss of suitable nesting trees through the

logging of large, old-growth stands and replacement with secondary growth and commercial

plantations is likely to contribute to a downturn in the owl’s range and abundance (NSW

Scientific Committee 2008). While the owl has shown itself capable of utilising some human-

altered or artificial habitats (Bradsworth et al. 2017), there still exists the risk of habitat

fragmentation as a result of extensive urban and suburban sprawl (NSW Scientific Committee

2008; Bradsworth et al. 2017; Carter et al. 2019). In the sub-urban environments around

Sydney, mortality due to either collision or electrocution has been estimated to be as high as

20% annually (BirdLife unpublished data). This could be increasing adult mortality past

thresholds that would push local populations toward exponential decline (McCarthy et al.

1999). In the Brisbane region, the amount of clearing for settlement has roughly doubled in

recent years (Technology and Innovation 2015). Within remaining forests there is evidence of

a decline in large, hollow-bearing trees due to past logging activities and repeated prescribed

burning (Eyre 2005; Eyre et al. 2010). Additional risks due to powerline collisions, pesticide or

rodenticide poisoning, and vehicle strikes (Grilo et al. 2020; Slater et al. 2020; Lohr and Davis

2018; Debus and Chafer 1994; NSW Scientific Committee 2008) are also present.

While forest clearing rates have increased dramatically in recent years in Australia (Evans

2016; Reside et al. 2017; Taylor 2015), much of that clearing has taken place outside the

Powerful Owl’s predicted area of occurrence (Evans 2016), with only approximately 1% of

these forests cleared since in the last 17 years (Ward et al. 2019). However, the summer

bush fires of 2019-2020 which burned more than 80,000 km2 of forest, impacted 31.5% of

the predicted area of occurrence of Powerful Owl (Clemens 2020). A separate recent paper

reviewing fire impacts estimated that approximately 23% of Powerful Owl habitat was

impacted (Ward et al. 2020). While we suspect that the recent BirdLife modelling is more

precise as it was focused solely on three species of owls and used predictor variables related

to these species such as forest cover, it highlights the uncertainty regarding the extent of

impact. It is also unclear how variable fire severity throughout these areas might have

resulted in population impacts (Ward et al. 2020), but old hollow-bearing trees would have

likely been at higher risk of being lost to fire (Salmona et al. 2018). Unfortunately, the

40

frequency and severity of fires are likely to be exacerbated by climate change (Cary and

Banks 2000; Williams et al. 2009). Drought-related dieback is also a growing threat associated

with drought and exemplified in Western Australia (Matusick et al. 2013; Hoffmann et al.

2019)

Powerful Owls require large old trees with large hollows to breed. Old growth tree loss will

likely be exacerbated as the climate changes with predicted increasing warm, dry days

leading to up to a 65% increase in fire danger in southeast Australia (Williams et al. 2009).

Increasing fire frequency and severity will likely further reduce available large hollows

(Salmona et al. 2018). Threats to old trees are increasing and include: droughts, fire, pests,

forest clearing for agriculture, road or infrastructure fire breaks, timber harvesting, and

climate change (Lindenmayer et al. 2016). There is a progressive decline in numbers of

hollow-bearing trees in production forests as logging rotations become shorter and as dead

stags collapse (Ball et al. 1999; Lindenmayer et al. 2012).

Table 8. Summary of Powerful Owl threats

Threat Impact Certainty Research priority

Management priority

Management feasibility

Principal source

Fire very high very high high high low Williams, et al. (2009), Salmona et al. (2018)

Drought medium medium high high low Lindenmayer et al. (2016), Matusick et al. (2013)

Climate change very high high high high low Williams et al. (2009)

Forest pests and pathogens

low low high high low Lindenmayer, et al. (2016)

Commercial logging

low medium low low low Taylor 2015

Forest Clearing high high medium high high Evans 2016

Rodenticides low low medium medium high Lohr and Davis (2018)

Automobile collision

medium medium medium low low Grilo et al. (2020)

Electrocution medium medium medium low high Slater, et al. (2020)

41

Australian Greater Sooty Owl Tyto tenebricosa tenebricosa


Robert Clemens, Nick Bradsworth, Holly Parsons, and Raylene Cooke.

Overview

The Australian Greater Sooty Owl is currently listed as Vulnerable in New South Wales, and

Threatened in Victoria. It is not listed under the EPBC Act, no recovery plan or federal

conservation advice has been drafted. IUCN status is currently at Least Concern and our

review did not uncover sufficient data to change that listing. Combined threats are suspected

to have impacted this species enough for listing, but evidence is lacking.

Table 9. Summary of Australian Greater Sooty Owl population



177,845 km2 169,000 km2 186,737 km2 Medium This document

Area of Occupancy



8,000 4,000 11,500 Medium BirdLife 2020

Generation Time

5.7 4.3 7.1 Low Bird et al. (2020)

Infraspecific taxa

Tyto tenebricosa arfaki of New Guinea is the only other recognised subspecies.

Taxonomic uniqueness: subspecies/species: 2, species/genus: 13, genera/family: 2,

families/order: 2.

Range

The Australian subspecies (tenebricosa) of Greater Sooty Owl (Tyto tenebricosa) is endemic

to eastern and south-eastern Australia, ranging from east-central Queensland south to the

Dandenong and Strzelecki ranges of Victoria (Bruce et al. 2020). Suitable habitat is lacking in

the Hunter Valley, so there appears to be a gap in this subspecies distribution in this area

(NSW Scientific Committee 2008). Subspecies occurs from coastal lowlands west towards the

tablelands and dividing range (NSW Scientific Committee 2008). Majority of range likely

occurs in New South Wales, where more than 5000 birds are estimated to occur (Garnett &

Crowley 2000).

Abundance



2020). Ongoing population decline is inferred from forest clearing (Evans 2016; Bruce et al.

2020), with modelling of recent intense and widespread bushfires in the summer of 2019-20

42

indicating over 40% of this species’ predicted area of occurrence was impacted (Clemens

2020). Threats across this owl’s range are likely leading to a significant loss of habitat. This

species’ difficulty of detection (Bruce et al. 2020) explains how a traditional “area of

occurrence” approach of using a (16 km2) grid over occurrence records results in a much

lower estimated AOO of 4,000 km2, while our MaxEnt approach accounts for survey bias and

doubles the more traditional estimate. The density of Sooty Owl across the range of

predicted suitable habitat is suspected to be lower than a maximum saturation with average

home range sizes, therefore placing the total population at under 10,000 mature individuals.

Ecology

The Australian Greater Sooty favours moist or wet forests, particularly rainforests, moist

eucalyptus forests, and gully forests with a dense mid- and understory (NSW Scientific

Committee 2008; Bruce et al. 2020). Eggs are laid in tree hollows up to 10 meters deep, and

30 centimetres or more in girth (NSW Scientific Committee 2008). Rock crevices and caves

are also used (Bruce et al. 2020). Breeding time varies, though typically between March and

April (HANZAB 2006). Lays 1-2 eggs (Bruce et al. 2020). Carnivorous, taking a range of

mammals, birds, insects, and others (NSW Scientific Committee 2008), though mammals

predominate (Bruce et al. 2020, HANZAB 2006).

Monitoring

A variety of monitoring has been undertaken at local scales over the years (HANZAB 2006).

Monitoring is opportunistic throughout much of the Australian Greater Sooty Owl’s range.

Threats

It is estimated that, historically, 37% of the Australian Greater Sooty Owl’s forest habitat has

been lost (Simmonds et al. 2019). While forest clearing rates have increased dramatically in

recent years in Australia (Evans 2016; Reside et al. 2017; Taylor 2015), much of that clearing

has taken place outside the Australian Greater Sooty Owl’s predicted area of occurrence

(Evans 2016), with only approximately 1% of these forests cleared in the last 17 years (Ward

et al. 2019). However, the summer bush fires of 2019-2020, which burned more than 80,000

km2 of forest, impacted 40.3% of the predicted area of occurrence of Australian Greater

Sooty Owl (Clemens 2020). A separate recent paper reviewing fire impacts estimated that

approximately 38% of Australian Greater Sooty Owl habitat was impacted (Ward et al. 2020).

While we suspect that the recent BirdLife modelling is more precise as it was focused solely

on three species of owls and used predictor variables related to these species such as forest

cover, it highlights the uncertainty regarding the extent of impact. It is also unclear how

variable fire severity throughout these areas might have resulted in population impacts

(Ward et al. 2020), but old hollow-bearing trees would have likely been at higher risk of being

lost to fire (Salmona et al. 2018). Unfortunately, the frequency and severity of fires are likely

to be exacerbated by climate change (Cary and Banks 2000; Williams, Bradstock et al. 2009).

Drought-related dieback is also a growing threat associated with climate change and

exemplified in Western Australia (Matusick et al. 2013; Hoffmann et al. 2019)

43

Greater Sooty Owls require large old trees with large hollows to breed. Old growth tree loss

will likely be exacerbated as the climate changes with predicted increasing warm, dry days

leading to up to a 65% increase in fire danger in southeast Australia (Williams et al. 2009).

Increasing fire frequency and severity will likely further reduce available large hollows

(Salmona et al. 2018). Threats to old trees are increasing and include: droughts, fire, pests,

forest clearing for agriculture, road or infrastructure fire breaks, timber harvesting, and

climate change (Lindenmayer et al. 2016). There is a progressive decline in numbers of

hollow-bearing trees in production forests as logging rotations become shorter and as dead

stags collapse (Ball et al., 1999; Lindenmayer et al., 2012).

Rodenticides (Lohr and Davis 2018), electrocution (Slater, et al. 2020), and automobile

collision (Grilo et al. 2020) are known threats to raptors.

Table 10. Summary of Australian Greater Sooty Owl threats


Management priority


Principal source






Commercial logging


Forest Clearing high high medium high high Evans 2016

Rodenticides low low low medium high Lohr and Davis (2018)


low low medium low low Grilo et al. (2020)

Electrocution low low medium low high Slater, et al. (2020)

44

Southern Masked Owl Tyto novaehollandiae novaehollandiae


Robert Clemens, Nick Bradsworth, Holly Parsons, and Raylene Cooke.

Overview

The Southern Masked Owl is currently listed as Vulnerable in New South Wales, Threatened

in Victoria, Endangered in South Australia, and a priority taxon in Western Australia. It is not

listed under the EPBC Act, no recovery plan or federal conservation advice has been drafted.

IUCN status is currently at Least Concern and our review did not uncover sufficient data to

change that listing. Combined threats are suspected to have impacted this species enough for

listing, but evidence is lacking.

Table 11. Summary of Southern Masked Owl population



177,845 km2 169,000 km2 186,737 km2 Medium This document

Area of Occupancy



8,000 4,000 11,500 Medium BirdLife 2020

Generation Time

5.7 4.3 7.1 Low Bird et al. (2020)

Infraspecific taxa

Nine subspecies, of which five in Australia (including T. n. galei, T. n. kimberli, T. n.

melvillensis and T. n. novaehollandiae) and four on islands to the north.

Taxonomic uniqueness: very high; subspecies/species: 9, species/genus: 13, genera/family: 2,

families/order: 2.

Range

Southern Masked Owls are found in both far south-west Australia and throughout forests of

southeast Queensland (Olsen 2002, HANZAB 2006). They are most common east of the Great

Dividing Range and are rarely observed more than 300 kilometres from the coast (Garnett

and Crowley 2000; HANZAB 2006). The most records of Southern Masked Owl have been

observed in New South Wales (Garnett and Crowley 2000).

Abundance



2020). Ongoing population decline is inferred from forest clearing (Evans 2016), with recent

modelling of intense and widespread bushfires in the summer of 2019-20 indicating that

40.3% of this species’ predicted area of occurrence was impacted (Clemens 2020). Threats

45

across this owl’s range are likely leading to a significant loss of habitat. Previous estimates of

the number of pairs were up to 400 in Victoria and up to 2000 in New South Wales (HANZAB

2006), with a total Australian population estimate of 7,000 mature individuals (Garnett and

Crowley 2000). The modelled estimates are larger than previous estimates. Southern Masked

Owls are not easy to detect, but they are widely thought to be rare in the wild. They are also

widely distributed in a variety of forests in southeast Australia, so it is possible that modelled

estimates indicate a more even density of distribution than is present.

Ecology

Southern Masked Owl breed and roost in hollows in large trees in a variety of forest types

(Garnett and Crowley 2000). Prey includes a variety of mammals, birds and lizards, but they

principally take terrestrial mammals. Breeding areas are often next to open areas where they

can hunt (HANZAB 2006). Breeding areas are generally associated with riparian areas and

pairs tend to occupy a home range from 5 to 10 km2.

Monitoring

A variety of monitoring has been undertaken at local scales over the years (HANZAB 2006).

Monitoring is opportunistic throughout much of Southern Masked Owl’s range.

Threats

Historically, 28% of Masked Owl forest habitat is estimated to have been lost (Simmonds et

al. 2019), but estimates are not available by sub-species. While forest clearing rates have

increased dramatically in recent years in Australia (Evans 2016; Reside et al. 2017; Taylor

2015), much of that clearing has taken place outside the Southern Masked Owl’s predicted

area of occurrence (Evans 2016), with only approximately 1% of these forests cleared in the

last 17 years (Ward et al. 2019). However, the summer bush fires of 2019-2020 which

burned more than 80,000 km2 of forest, impacted 32.2% of the predicted area of occurrence

of Southern Masked Owl (Clemens 2020). Unfortunately, the frequency and severity of fires

are likely to be exacerbated by climate change (Cary and Banks 2000; Williams, Bradstock et

al. 2009). Drought-related dieback is also a growing threat associated with climate change

and exemplified in Western Australia (Matusick et al. 2013; Hoffmann et al. 2019).

Southern Masked Owls require large old trees with large hollows to breed. Old growth tree

loss will likely be exacerbated under climate change, with predicted increasing warm, dry

days leading to up to a 65% increase in fire danger in southeast Australia (Williams et al.

2009). A separate recent paper reviewing fire impacts estimated that approximately 15% of

Masked Owl habitat was impacted (Ward et al. 2020). However, a larger proportion of this

impact would have been felt by the Southern Masked Owl, as the fires occurred primarily

within this subspecies’ habitat. While we suspect that the recent BirdLife modelling is more

precise as it was focused solely on three species of owls and used predictor variables related

to these species such as forest cover, it highlights the uncertainty regarding the extent of

impact. It is also unclear how variable fire severity throughout these areas might have

resulted in population impacts (Ward et al. 2020), but old hollow-bearing trees would have

46

likely been at higher risk of being lost to fire (Salmona et al. 2018). Increasing fire frequency

and severity will likely further reduce available large hollows (Salmona et al. 2018). Threats to

old trees are increasing and include: droughts, fire, pests, forest clearing for agriculture, road

or infrastructure fire breaks, timber harvesting, and climate change (Lindenmayer et al.

2016). There is a progressive decline in numbers of hollow-bearing trees in production

forests as logging rotations become shorter and as dead stags collapse (Ball et al., 1999;

Lindenmayer et al., 2012).

Rodenticides (Lohr and Davis 2018), electrocution (Slater, et al. 2020), and automobile

collision (Grilo et al. 2020) are known threats to raptors. The Masked Owl is not adapting to

sub-urban environments.

Table 12. Summary of Southern Masked Owl threats


Management priority


Principal source






Commercial logging


Forest Clearing high high high high high Evans 2016

Rodenticides medium medium medium medium high Lohr and Davis (2018)


low low medium low low Grilo et al. (2020)

Electrocution low low medium low high Slater, et al. (2020)

47

Comparisons of forest plots near Powerful Owl breeding and

random locations

An exploratory investigation was

made into the differences between

Powerful Owl breeding locations

and randomly selected locations

within the Powerful Owls range.

Specifically, we wanted to identify

the average and minimum forest

patch size used at Powerful Owl

breeding sites. We also wanted to

explore if forest patches at

Powerful Owl breeding sites

differed significantly from random

areas. This will build on our

growing understandings of Powerful

Owl habitat requirements (Kavanagh

1997, Loyn et al. 2001).

Methods

Records that indicated active breeding in Birdata (BirdLife Australia 2020) were collated,

plotted and a 1km buffer was generated around each point in ArcGIS. Evidence of breeding

included a nest hollow location, breeding behaviour, juveniles sighted, or a group of three or

four owls sighted in an area. In well sampled areas overlapping buffered points were

eliminated by removing overlapping areas where evidence of breeding location was weaker,

and in areas where the evidence was equal, areas were removed randomly. The clearest

records of breeding locations were breeding hollows, followed by recently fledged young,

and breeding behaviour. In areas outside the data rich areas of Sydney and Brisbane non-

overlapping areas were retained if three or four Powerful Owls were recorded in winter or

spring. This left 190 non-overlapping breeding areas ~314 ha in size.

A set of 190 randomly selected locations was then selected that was at least two kilometres

from the breeding plot centroids but no more than 20km from a centroid. This was done by

generating a merged 20km buffer around each breeding centroid, then subtracting a 2km

buffer from those polygons, and creating random points within the remaining polygons. Each

of the random points was then buffered by 1km resulting in a second set of 190 random

areas ~314 ha in size.

Four variables were summarised within each random and breeding plot. The first variable

was total forest cover where forest classes of closed forest, rainforest, woodland and open

Photo: Powerful Owl, male, female and chick;

Amanda Robertson

48

woodland were reclassified into one forest class (ABARES, 2019). Annual rainfall was then

totalled from each plot (Vanderwal, 2012). The average plot elevation was then calculated

from a 9 second DEM (Geoscience 2008). Finally, the length of all streams within each plot

was calculated to represent stream density.

Plots were then imported into RStudio (RStudio Team 2015, R Core Team 2018), data was

then extracted and either totalled, or averaged using the following packages: ‘raster’

(Hijmans 2017), ‘rdgal’ (Bivand et al. 2018), and ‘dplyr’ (Wickham et al. 2019).

Results

Breeding plot had significantly more forest cover, more annual rainfall, and were at lower

elevations than random plots (Figure 8). The density of streams was not significantly different

at breeding and random plots.

Breeding plots had a median of 59% of the plot covered in forest or 187 ha of forest in a 314-

ha plot. Random plots had a median of 21% of the plot covered in forest or 65 ha of forest in

a 314-ha plot. Forest cover in breeding plots ranged from 15 ha to 314 ha, while random

plots ranged from 0 to 314 ha. Only two breeding plots had less than 30 ha of forest, and only

five of the 190 has less than 50 ha of forest. Breeding locations with less than 50 ha of forest

were not places where breeding hollows were identified, so it is possible these locations

were simply ones that juveniles dispersed to soon after breeding. In Queensland, all breeding

locations had more than 50 ha of forest. However, based on Google Earth imagery there

were two locations where the patch of contiguous forest around the breeding hollow was

only ~30-ha in size, but these areas had forested corridors joining the breeding patch to

other larger patches of forest, and housing in the area was low density with many trees. We

did not assess how low-density housing with many trees was classified in the forest layers

and this is something as well as connectivity that should be explored further. Together the

available evidence indicates that breeding in southeast Queensland is unlikely to occur in

areas with less than 50 ha of forest habitat, and is more common in areas where over ½ of

the area is forested.

It was surprising to find that annual rainfall was higher in breeding areas than in random plots

no more than 20km away, but it is likely that forested areas have higher rainfall totals. The

finding that Powerful Owl were found at significantly lower elevations than random sites is

consistent with the idea that Powerful Owl are found predominantly in low-land or bottom

land forest. However, there is scarce sampling for Powerful Owl at higher elevations, so it is

possible that this finding relates to sampling bias. It was also surprising that stream density

was not significantly higher in breeding plots, but this analysis did not distinguish between

streams that flow regularly, and those that are usually dry. We would expect Powerful Owl to

be found more regularly near streams that flow more regularly.

49

We will continue to explore the habitat characteristics associated with breeding sites, and

breeding success. We expect some improvements by only using breeding locations where the

breeding hollow has been located, and by collecting some vegetation data at plots centered

on breeding hollows and random locations.

Figure 8. Comparisons of Poweful Owl breeding plots and random plots 2km to 20 away from

breeding locations all ~314 ha in size. A = comparisons of total forest cover significantly different

Mann-Whitney U p-value < 0.001; B = comparison of totalled annual rainfall significantly different

Mann-Whitney U p-value < 0.001; C = comparison of elevation significantly different Mann-Whitney

U p-value < 0.001; D = comparison of stream density showed no significant differences.

50

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Appendix A. Powerful Owl Project Volunteer Survey Results 2020

58

What changes would you like to see in the project? Since all other owls now look outnumbered by Powls it would be great to expand the program to all other owls. I think I would like see survey information from the other surveys in assigned areas such as cabbage tree creek, bunyaville and one mile creek, cashmere

Communication is improving but i would like some support on printing copy of information to deliver to residents etc. The project itself was great!

I rather suggest something in the next season as I just joined the project.

More interaction between those just starting out in the project and those with experience. I know COVID-19 made it difficult for face to face, but there was a lack of interaction at other levels, such as email, online meetings it even phone calls. None

Excellent as is

Totally happy with it. Nothing needs changing.

We are very happy with the project.

More organised survey walks with experienced people

Perfect as is.

None

More information about recording the data and trouble shooting

None that I can think of

Better training, compulsory training and rudimentary certification, more objective and transparent protocols which must be signed off on by all members, more involvement in the development of protocols particularly those pertaining to ethics, somewhat more academic output, much less emphasis on photography on social media groups, better networking including perhaps a dedicated website with portal, significant improvement of the Birdata app (including controls which default to private lists for P Owl project observations), more advanced management structure The BirdData app via which we record our sightings sometimes doesn’t seem to reliably work with all locations (e.g., D’Aguilar NP, or Mt Coot-tha forest don’t come up via the location search). Many times, I’ve gone to enter sightings or calls heard, but the App seems stuck on locations near Sydney- even when I ensure my phone’s GPS is on... Sign up and form filling is cumbersome and not user friendly

more information passed between participants in each small area

59

Covid really killed off my participation this year. Notwithstanding that I would have undertaken more surveys if I had linked up with more people. Get some social benefit. There was always talk of linking up people but it never happened. It is a pretty inconvenient assignment; going out on dusk (dinner time) and not actually doing much walking but going to places that one would not normally walk. None

Perhaps a twice a year meeting of smaller (area-territory) would improve communication and knowledge on a local level. Perhaps a twice a year meeting of smaller (area-territory) would improve communication and knowledge on a local level. Recording of sightings of a known pair is a valid part of the project, rather than surveying for new territories. More volunteers involved.

I would like the project to continue throughout the Summer to learn more of the outcome of owlets (mortality vs survival rates). Nothing to add

Nothing to add

What could we do to increase the benefits of participating? Great project, exceeded any expectations, nothing comes to mind how this could be even better.

I don't think I need additional benefits

Some more support connecting residents and work with government especially QLD

It feels inspiring when I hear or see an owl, so knowing where it is most likely to find an owl

Look for other birds as well once the PO sometimes is not present. It would be a way to keep people engaged.

More interaction

More events once covid allows to bring more people together

No extra benefits needed

Nothing

Have several organised local surveys after the training

Happy as is.

None

Have a T Shirt for the project.

Perhaps some personal accounts of joys of seeing the owls

Certification for members who complete training and familiarise themselves with protocols, opportunities for official middle management positions

Set up a private FB page

be more informative with what was seen/heard in each survey area

Doing a good job now.

As mentioned, I think encouraging closer contact with other participants in a smaller area or by suburb, for instance, West Logan, East Ipswich, McDowell etc. would bring benefits.

Some organised field trips to known nest sites

Add extra hours to the day - you guys are great, life is a struggle, wish I could help more

More workshops

I would very much like to have a positive sighting

End of season social gathering perhaps (though difficult to implement at the current time)

End of season social gathering perhaps (though difficult to implement at the current time)

More group meetings :)

60

What kind of further field training would you like? Once first owl is found no further training needed.

I'm good - just being able to ask questions of Rob/Matt/Jasmine is enough

How to use the recording machine

Identification of material in pellets

Recognize better PO environment and used resources (trees that would work as a nest). It would be nice to try to set up a quiz with the different birds and calls so we could feel more confident to identify species.

More on identification of calls, types of hollows to look for and other nocturnal animals

Habitat I guess

Would like to know more about calls of other night creatures that I might hear when I am in the field

Learning skills to help us identify other birds we see or hear on our surveys would be very helpful.

More walks with people who know how to find the owls

NA

None

Are we allowed off tracks?

Not applicable

Field training needs to be more formalised, should be compulsory, and trainees must be assessed much more thoroughly for their understanding.

Go out with experienced spotters

None

I think more, maybe shorter field visits could be considered. For example, visit a site that contains some wash to show the general layout of the areas the Owls like to roost could be of assistance. It has been my experience that newer researchers concentrate too much on trying to spot the Owls roosting instead of looking for signs they are actually in the area first.

bush safety e.g. snake bite response.

Capacity to form local groups

Just more info grams in emails

To accompany experienced researchers on field trips. More workshops.

Nothing to add

Nothing to add

Some recordings of Baby Powerful Owls

61

What have you learned from the project? It was an eye opener. Before visiting first workshop I was of an opinion Powerful Owls are rare and impossible to find, as opposed to Southern Boobooks, but in fact in Redlands I now there are more Powls than any other owl.

a lot about p'owl behaviour and calling (and other ninox owls) and what constitutes p'owl habitat.

Where to look for powerful owl.

A lot about owls, and a deeper understanding of the natural areas that I've surveyed in.

The importance of communication with everyone involved in the project, whether it be in the field or in volunteer engagement. Patience; more often than not having to hear signs of Powerful Owl presence later in the evening. Tracking/problem solving; having to observe canopy coverage with types of trees, other bird behaviours, creek direction, whitewash and feathers to find the likely location of the owls. The importance of following a survey/data entrance routine. How to Identify different species within each forest.

Habits of PO and other nocturnal birds.

That there are different owls which can be identified by calls as well as visible features.

Powerful owl info.

Everything about the owls

So much about owls!

Patience

Did learn some information about owls

Powerful owls are difficult to spot

Pretty much everything we know about owls.

More about birds, owls especially. The range of places they can be found in.

Different owls, bird behaviours, different birds,

More about nesting habitat to look out for

That there are far more Powerful Owls in SEQ than previously thought

Powerful owl habitat and behaviour including breeding times

Patience

That the Owls are initially hard to find but once found I think a pattern of observing them can be worked out without intruding too much on their territory.

Bird calls, how to spot POWLS.

More aware of the ecology of my local pair of owls

About different types of aussie owls

Learning about habitat and owl territories amongst many other things.

The timing of owlets fledging

Owl ecology and habits

Owl ecology and habits

Trees

62

Is there anything else you would like to learn? Purely, because I am Redlands local, I would like to know if there are any other owl active?

I'd like to know more about how and why they communicate with each other

Interact with residents nearby of the habitat and spread awareness of the owl habitats.

How the occurrence of every animal species or vegetation type helps each other and how they influence Powerful Owl occurrence

No

More on the daily routine of the owls

Nothing in particular that can't be discovered through further field work.

Unsure - probably more about the relationship between owls, environment and protection

No

The best way to find owls

How long should we continue to monitor the group after the young have fledged? Is it better to just note where they appear to have settled while teaching the young, before separating, and moving back towards the nest tree for the breeding season or do we still need to study them in the â€œin between periodâ€ before they start the mating season again?

Where they nest and how we can secure future nesting options.

Always learning and open to new experiences.

More about owlets after fledging.

Nothing to add

Nothing to add

64

What improvements would you suggest for the workshops or reference materials? further encouragement for people to actually get out and do surveys

Let us know if we should report other birds at the PO survey option. Some description of the area being surveyed were a bit complicated.

More learning in the field.

Haven't been to one due to covid

None

No problems

Clearer maps

Can't think of any

Reference material must be subject to revision, must be transparent and accessible at any time through a common portal, and must supplement field training.

All OK

The workshops, in general are very good. I think we should be considering the shorten indoor presentation combined with some sort of field work. I would like to see a QR code, or similar, linked to Owl calls on all material handed out so that the public can immediately reference the calls when reading things like our letterbox leaflet.

More field-based workshops where possible

powerful owl project in southeast queensland progress report

Documents