Department of Sustainability, Environment, Water, Population and
Communities
Carnaby's Cockatoo Population Viability
Analysis Model Report
11 November 2013
Document information
Client: Department of Sustainability, Environment, Water, Population and Communities
Title: Carnaby's Cockatoo Population Viability Analysis Model Report
Document No: 2189220A PR_0164
Date: 11 November 2013
Rev
Date
Details
A
30/05/2013
Draft Report
B
19/06/2013
Final Draft
C
21/08/2013
Final Report
D
11/11/2013
Final Report (minor edit)
Author, Reviewer and Approver details
Prepared by:
Lawrie Conole, Evan Pickett
Date: 05/08/2013
Signature:
Reviewed by:
Toby Lambert
Date: 11/11/2013
Signature:
Approved by:
Alex Cockerill
Date: 11/11/2013
Signature:
Distribution
Department of Sustainability, Environment, Water, Population and Communities, Parsons Brinckerhoff file, Parsons
Brinckerhoff Library
©Parsons Brinckerhoff Australia Pty Limited 2013
Copyright in the drawings, information and data recorded in this document (the information) is the property of Parsons
Brinckerhoff. This document and the information are solely for the use of the authorised recipient and this document
may not be used, copied or reproduced in whole or part for any purpose other than that for which it was supplied by
Parsons Brinckerhoff. Parsons Brinckerhoff makes no representation, undertakes no duty and accepts no
responsibility to any third party who may use or rely upon this document or the information.
The views and opinions expressed in this publication are those of the authors and do not necessarily reflect those of
the Australian Government or the Minister for Sustainability, Environment, Water, Population and Communities. While
reasonable efforts have been made to ensure that the contents of this publication are factually correct, the
Commonwealth does not accept responsibility for the accuracy or completeness of the contents, and shall not be
liable for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the
contents of this publication.
Document owner
Parsons Brinckerhoff Australia Pty Limited
ABN 80 078 004 798
Level 5 503 Murray Street
Perth WA 6000
PO Box 7181
Cloisters Square WA 6850
Australia
Tel: +61 8 9489 9700
Fax: +61 8 9489 9777
Email: perth@pb.com.au
www.pbworld.com
Certified to ISO 9001, ISO 14001, AS/NZS 4801
A GRI Rating: Sustainability Report 2011
Funded by the Department of Sustainability, Environment, Water, Population, and
Communities through the Sustainable Regional Development Program
Creative Commons
This report is licensed under Creative Commons Attribution 3.0 Australia licence
(http://creativecommons.org/licenses/by/3.0/au/deed.en).
Cover photo credit
Carnaby’s Cockatoo, Bindoon. (T Kirkby 2005).
Recommended citation
Cockerill, A., Lambert, T, Conole, L. and Pickett, E. (2013). Carnaby's Cockatoo Population Viability Analysis
Model Report. Report funded by the Department of Sustainability, Environment, Water, Population, and
Communities through the Sustainable Regional Development Program. Parsons Brinckerhoff, Perth.
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Contents
Page number
Glossary
iii
Executive summary
vi
1.
1
2.
3.
4.
Introduction
1.1
Rationale for development of a Carnaby’s Cockatoo PVA
1
1.2
Acknowledgements
2
Methodology
5
2.1
Personnel
5
2.2
Literature review
5
2.3
Modelling approach
5
2.4
Population biology parameters
7
2.5
Test group and peer review of PVA
8
2.6
Assumptions of the PVA model
9
Modelled scenarios
17
3.1
Scenario summary
17
3.2
Scenario assumptions
19
3.3
Simulated population trajectories
19
Discussion
21
4.1
Scenario analysis
21
4.2
Research questions
23
4.3
Data gaps and future research priorities
26
5.
Conclusion
27
6.
References
A-1
Parsons Brinckerhoff | 2189220A PR_0164 i
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
List of tables
Table 2.1
Table 2.2
Table 2.3
Table 3.1
Study team
Summary table for comparison of PVA platforms
PVA parameters used in development of the PVA models
Conversion of hypothetical development scenarios to PVA parameters
5
6
7
17
List of figures
Page number
Figure 1.1
Figure 1.2
Figure 2.1
Figure 2.2
Figure 2.3
Figure 2.4
Figure 2.5
Figure 3.1
Figure 3.2
Recorded distribution of Carnaby’s Cockatoo
Location of Perth and Peel regions
Regression of age structure data technique for determining survival from an age
distribution (Skalski et al. 2005)
Distribution of age classes in Carnaby’s Cockatoo (100,000 bootstrap iterations)
Impact of different mortality regimes on projected population of Carnaby’s
Cockatoo. Y-axis represents proportion of the initial population size.
Sensitivity testing of Scenario 1 with three estimates of the proportion of Carnaby’s
Cockatoo pairs that can breed in a given year (10%, 16% and 30%). Y-axis
represents proportion of the initial population size.
Comparison of scenarios with different starting populations/carrying capacity (Pop)
and breeding systems. Y-axis represents proportion of the initial population size.
‘All breeding’ is where 100% of the females can breed. Reproductive carrying
capacity means that at high density, only a proportion (30%) can breed each year.
Mean expected population sizes for the Carnaby’s Cockatoo under the first two
(Scenario 1, Scenario 2) of six management scenarios. Y-axis represents
proportion of the initial population size.
Mean expected population sizes for the Carnaby’s Cockatoo under four (Scenario
3, Scenario 4, Scenario 5 and Scenario 6) of six management scenarios. Y-axis
represents proportion of the initial population size.
3
4
10
11
12
14
15
20
20
List of appendices
Appendix A
Appendix B
Modelling scenarios
Literature review
Parsons Brinckerhoff | 2189220A PR_0164 ii
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Glossary
Abundance
A measure of the number of individuals in a community
Biodiversity
The biological diversity of life is commonly regarded as being made up of the
following three components:
1.
Genetic diversity — the variety of genes (or units of heredity) in any
population.
2.
Species diversity — the variety of species.
3.
Ecosystem diversity — the variety of communities or ecosystems.
Bioregion (region)
A region defined by physical and biotic characteristics in a national system as
defined in the Interim Biogeographic Regionalisation for Australia (Thackway &
Cresswell 1995).
Breeding
The multiplying of animals through sexual or asexual reproduction.
Brood
The collective description of a bird’s young during a single nesting event.
Carrying Capacity
The maximum population size of a species that the environment can sustain
indefinitely.
Demographic
A collective group of individuals within a population that are grouped by one or
more attributes in common.
Department of
Environment and
Conservation (DEC)
Western Australian state government department that regulates matters related
to environment protection. DEC has recently become the Department of Parks
and Wildlife (DPaW).
Department of
Sustainability,
Environment, Water,
Population and
Communities
(SEWPaC)
The Australian Government department that develops and implements national
policy, programs and legislation to protect and conserve Australia’s natural
environment and cultural heritage and administers the EPBC Act.
Dispersal
The spreading movement of organisms away from a place of birth, breeding,
foraging or roosting aggregation.
Ecological community
An assemblage of species occupying a particular area.
EPBC Act
Commonwealth Environment Protection and Biodiversity Conservation Act
1999.
Exotic
Introduced from outside the area.
Fecundity
A measure of an organism’s ability to reproduce.
Fledging
A baby bird’s first growth stage where it is partly or wholly feathered and where
it is usually still bound to the nest.
Founder effect
The founder effect is a special case of genetic drift, occurring when a small
group in a population splinters off from the original population and forms a new
one. The new colony may have less genetic variation than the original
population, and differ in other characteristics.
Habitat
An area or areas occupied, or periodically or occasionally occupied, by a
species, population or ecological community, including any biotic or abiotic
components.
Parsons Brinckerhoff | 2189220A PR_0164 iii
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Habitat restoration
Creation of new habitat in previously cleared areas, or improvement of habitat
quality in disturbed areas of habitat.
Hypothetical
Assumed to exist in a circumstance that is not proven.
Indigenous
Native to the area: not introduced.
Introduced
Not native to the area: not indigenous. Refers to both exotic and nonindigenous Australian native species of plants and animals.
In situ
Existing in its natural place without manipulation.
Key Threatening
Processes
A process that threatens, or could threaten, the survival, abundance or
evolutionary development of native species, populations or ecological
communities). Key threatening processes are listed under the EPBC Act.
Capitalisation of the term ‘Key Threatening Processes’ in this report refers to
those processes listed specifically under the legislation.
Life history parameters
Data which describe the major life history characteristics of the species, such
as mortality, fecundity, age at sexual maturity, etc.
Likely
Taken to be a real chance or possibility.
Locality
The area within a 10 km of the site.
Mean
The mathematical average of a group of numerical values. The most commonly
utilised measure of the central tendency of a group of numbers calculated as
the sum of a group of numbers divided by the count of numbers in that group.
MNES
Matter of National Environmental Significance listed under the EPBC Act.
Mortality
A measure of a population’s death rate.
Population
A group of organisms with the capacity to exchange genetic information.
Population Viability
Analysis (PVA)
The bringing together of a species’ characteristics with environmental variability
to forecast population health and extinction risk. Usually unique to each
species population.
Recovery plan
A plan prepared to assist the recovery of a Threatened species, population or
ecological community.
Reproduction
The process by which new living individuals are produced from existing living
individuals.
Reproductive density
dependence
Negative density-dependence, or density-dependent restriction, describes a
situation in which population growth is curtailed by crowding, predators and
competition.
Return rate
The measure of a population’s individuals that repeat a movement to a place
within a set period of time, e.g. seasonally, annually or longer period of time.
Known marked birds which return to traditional, monitored nest sites.
Scenario
An imagined set of circumstances that may or may not be based on real events
Sensitivity analysis
A study of how predictable a model is (e.g. PVA) by measuring the reliability of
the data sets used to generate the model.
Sex ratio
The comparative measure of male and female individuals in a population or
population demographic.
Significant
Important, weighty or more than ordinary.
Parsons Brinckerhoff | 2189220A PR_0164 iv
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Sink population
Source-sink dynamics is a theory that suggests there are source areas (high
quality habitat that on average allows the population to increase) and sink
areas (low quality habitat that on its own would not be able to support a
population). If an excess of individuals produced in the source frequently
moves to the sink, the sink population can persist indefinitely.
Spatial analysis
The mathematical study of a species’ patterns of distribution.
Standard deviation
A statistical concept describing how much variation exists around the average
(mean). Low standard deviation indicates that the data points tend to be close
to the mean; high standard deviation indicates that the data points are widely
spread.
Stochastic
In relation to environmental events – those that are random and cannot be
predicted e.g. severe drought or rainfall events.
Sustainable Regional
Development (SRD)
Program being undertaken in selected high-growth regions in Australia by
SEWPaC. The program will enable a more strategic approach to the
management and protection of MNES in partnership with state and local
governments.
Threatened biodiversity
Threatened species, populations or ecological communities as listed under the
EPBC Act.
Threatened species,
populations and
ecological communities
Species, populations and ecological communities listed as Vulnerable,
Endangered or Critically Endangered (collectively referred to as Threatened)
under the EPBC Act. Capitalisation of the terms ‘Threatened’, ‘Vulnerable’,
‘Endangered’ or ‘Critically Endangered’ in this report refers to listing under the
Commonwealth EPBC Act.
Trend
The tendency of a data set to increase or decrease in value.
Viable local population
A population that has the capacity to live, develop and reproduce under normal
conditions, unless the contrary can be conclusively demonstrated through
analysis of records and references.
VORTEX
A statistical software package designed to generate Population Viability
Analyses.
Weed
A plant growing out of place or where it is not wanted: often characterized by
high seed production and the ability to colonise disturbed ground quickly.
Weeds include both exotic and Australian native species of plant naturalised
outside of their natural range.
Parsons Brinckerhoff | 2189220A PR_0164 v
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Executive summary
Preamble
As part of the Australian Government’s sustainable population strategy, the Sustainable Regional
Development (SRD) program is being undertaken in selected high-growth regions. The program will enable a
more strategic approach to the management and protection of matters of national environmental significance
(MNES) in partnership with state and local governments. Regional sustainability planning in up to seven
regions will be undertaken across Australia in regional areas of high economic growth. The Perth and Peel
regions in Western Australia are one of these areas of focus.
The purpose of projects being funded under the SRD program is to provide information to support the
strategic assessment of the Perth and Peel regions. The strategic assessment is being undertaken in
partnership between the Australian Government and Western Australian Government and will examine the
impacts of future urban development on MNES.
A key species potentially impacted by economic growth in the Perth and Peel regions is Carnaby’s BlackCockatoo Calyptorhynchus latirostris, an Endangered species protected under the Environment Protection
and Biodiversity Conservation Act 1999 (EPBC Act). This species is known widely in Western Australia as
Carnaby’s Cockatoo and as such will be referred to in this document using this localised terminology.
As part of the strategic assessment further detailed information on Carnaby’s Cockatoo population viability is
required. The use of a Population Viability Analysis, or PVA model, can contribute to the scientific evidence
base to inform effective decision making about the conservation of the species and land use planning.
The Carnaby’s Cockatoo PVA process
Parsons Brinckerhoff has been commissioned by the Australian Government Department of Sustainability,
Environment, Water, Population and Communities (SEWPaC) to provide the Carnaby’s Cockatoo PVA. The
process of preparing the PVA has involved three main stages:



Task 1 – Preparation of a Carnaby’s Cockatoo scientific literature review from published and
unpublished sources as well as incorporating expert knowledge (Parsons Brinckerhoff, 2013) (see
Appendix B).
Task 2 – Preparation of peer-reviewed Population Viability Analysis model (PVA) for Carnaby’s
Cockatoo (discussed in this report).
Task 3 – Using information from Task 1 and the PVA model prepared in Task 2, identify critical life
history parameters for Carnaby’s Cockatoo, identify parameter sensitivities to data variability, and test
development and conservation scenarios in the Perth-Peel Strategic Assessment to provide an
indication of likely trends in relation to each scenario (provided in this report).
Parsons Brinckerhoff | 2189220A PR_0164 vi
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
The Carnaby’s Cockatoo PVA report
The specific research questions discussed in this report are:

What are the critical life history parameters of Carnaby’s Cockatoo?

Which parameters are sensitive to data variations?

What is the significance of any potential loss of habitat in the Perth and Peel regions and the resulting
impact on population viability using different development and conservation?
The PVA model will assist the consideration of various options for land use in relation to impacts upon the
Carnaby’s Cockatoo population, and the results will be incorporated into the strategic assessment for the
region. This PVA predicts change trends in the population of Carnaby’s Cockatoo from a baseline point, and
tests for sensitivity of the model to a number of changes in breeding and feeding habitat and variation in
breeding and mortality rates. The PVA model is intended for continuous use and refinement in the future.
This report has been informed by a review of scientific literature related to Carnaby’s Cockatoo.
The literature review was undertaken in association with an expert workshop to determine the latest
information to use as inputs into the PVA. This document outlines how the PVA was created and then
outlines what the PVA predicts would eventuate under six hypothetical habitat modification scenarios.
Important PVA limitations
Although the PVA and scenarios tested have been developed based on the most current and relevant
scientific literature available for Carnaby’s Cockatoo, it is importantly acknowledged that there are still many
uncertainties in the understanding of Carnaby’s Cockatoo ecology. It is therefore important to consider the
outcomes of the PVA and modelled scenarios as indicators of approximate trends rather than exact
outcomes. It is also the case that environmental and demographic stochasticity have not been explicitly
modelled in this PVA as suitable data were not available.
Further research is recommended to enable improvement of the PVA model reliability by future users and to
enhance understanding of Carnaby’s Cockatoo in general to aid in recovery of the species. The PVA and its
scenarios are based on a number of assumptions due to a lack of available data. The general trends
identified in this report are however still useful for conservation strategic planning. Further development of
the model once additional data becomes available in the future will allow for a more robust and useful model.
Scenario analysis
Scenario 1 assesses the hypothetical impacts upon Carnaby’s Cockatoo if clearing of habitats were to cease
immediately, and existing habitats were protected but not enhanced. The results show that the existing
population would remain at relatively stable numbers, although the lag time between habitat removal and
population stabilising means that even if clearing ceased immediately, the population is still likely to decline
for a period due to the long-lived nature of the species.
Scenario 2 models the situation where clearing of habitats does not cease immediately and is not offset by
habitat restoration. The overall trend shown for this scenario indicates a sustained reduction in the
population size over the 20 year period in which clearing of habitat is modelled to occur in the Perth and Peel
regions. A general trend towards extinction of the northern sub-population in 20 years is considered likely if
clearing occurred without adequate conservation response.
Scenario 3 assumes that removal of habitat for urban development, basic raw material extraction and nonreplacement of pine plantations would continue to occur as in Scenario 2. However habitat
creation/restoration would also occur. The modelling of this scenario shows a slow recovery over a period of
Parsons Brinckerhoff | 2189220A PR_0164 vii
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
around 25 years to what is likely to be a relatively stable population. This assumes restoration of vast areas
of both native and pine habitats to a condition similar to existing good quality habitat.
Scenario 4 is modelled to understand the impact if all conservation effort is focussed on breeding success,
but there is loss of foraging habitat. This scenario shows that the species could not recover based on
improvement of breeding habitat alone. In this instance the availability of foraging habitat would be the
limiting factor for the carrying capacity.
The objective of Scenario 5 is to understand the impact of a hypothetical area to be cleared for urban
development in the Perth and Peel regions (after avoid and mitigate is implemented) in combination with
potential restoration of foraging and breeding habitat being implemented. The trend shown shows an
increase in the population to pre-clearing levels over a period of around 20 years. This assumes substantial
investment occurs in foraging and breeding habitat restoration in association with existing habitat
conservation.
The objective of Scenario 6 is to assess the hypothetical impact if the area of clearing used in Scenario 5 is
reduced by using consolidated urban form, partial retention of pine plantations and avoidance of basic raw
material extraction (through reduction in demand). The apparent difference between Scenario 5 and this
scenario is that again this scenario starts from an even higher base point than Scenario 5 because more of
the existing habitat has been avoided and conserved. This shows that the species can more easily recover if
foraging and breeding habitat are restored. Of all the scenarios, this consolidated urban form scenario
appears to provide the best outcome for the population apart from Scenario 1.
Research questions
Critical life history parameters are considered to be those parameters that are likely to more strongly impact
population viability. It is these life history parameters that need to be focussed on to work towards a viable
species population scenario. The following parameters are considered to be critical for management of the
species:

breeding success (fecundity)

breeding habitat availability and location

foraging habitat availability and location

hollow abundance and annual rates of loss or degradation

mortality

age structure.
Assumptions about the proportion of Carnaby’s Cockatoo pairs that can breed in a given year (10%, 16%
and 30%) lead to variability and uncertainty in the PVA model outputs. Whilst the impact of 16% and 30%
estimates on the model run for Scenario 1 are similar, an estimate of 10% leads to a greater impact for
Scenario 1 on the population of Carnaby’s Cockatoo in the Perth and Peel regions.
The PVA is sensitive to the proportion of Carnaby’s Cockatoo pairs that can breed in a given year parameter,
and therefore refinement of this parameter should be a high order priority for future research and PVA model
development.
The trend shown in the modelled Scenarios 2 and 4 confirm that loss of foraging habitat in the Perth and
Peel regions will have a negative impact on the population size of Carnaby’s Cockatoo, and that restoration
attempts which include measures to improve breeding success without concomitant foraging habitat
availability will fail to produce satisfactory rates of recovery.
Parsons Brinckerhoff | 2189220A PR_0164 viii
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Recommendations
This report identifies future research priorities that would assist in the further development of the Carnaby’s
Cockatoo PVA and reduce uncertainty in some parameters. These include research to refine several of the
PVA’s primary inputs:

identification of reliable estimates for the total extant population and sub-populations

identification of a reliable figure for the proportion of Carnaby’s Cockatoo pairs that can breed

quantification of nest hollow abundance and annual rates of loss or degradation in breeding habitats

documenting the increase in breeding success where additional nest hollows are provided

refining mortality knowledge through further directed research and opportunistic data collection

refining knowledge of age structure of the population through further directed research and opportunistic
data collection


quantification of numbers and origin of Carnaby’s Cockatoo directly reliant on the plantation pine habitat
research should also be conducted on habitat quality of different vegetation types and food plant
species.
It is also recommended that research to address limitations of the current PVA (which does not consider
spatial and temporal variability and environmental stochasticity) be prioritised:

generation of long-term demographic models to enable incorporation of stochastic impacts on the
population

pursuit of spatial analysis of discreet local populations including dispersal between these populations.
Conclusions
The PVA has enabled the identification of many data gaps, which could form the basis of future research
focus for Carnaby’s Cockatoo. This is a reflection of the value of the current Carnaby’s Cockatoo PVA in
pointing to parameter sensitivities and data gaps.
The PVA is sensitive to the proportion of Carnaby’s Cockatoo pairs that can breed in a given year parameter,
as well as the estimate of post-fledging survival. Therefore refinement of these parameters should be a high
order priority for future research and PVA model development.
As the population of Carnaby’s Cockatoo is assumed to be functioning at close to the foraging and
reproductive carrying capacity, it is unsurprisingly the case that development scenarios which result in a loss
of either foraging or breeding habitat have a negative impact on the population size trend.
It is possible that the current population is continuing to experience decline due to past habitat degradation
which in turn reduces carrying capacity. If this is the case, the population trajectories from further clearing
scenarios will have a larger effect than is predicted by this PVA model.
The scenarios outlined and modelled in Section 3 only provide a general indication of trends for each of the
hypothetical scenarios. The greatest value of undertaking a PVA is for this reason, however due to the
complex interaction of PVA parameters of varying reliability, focus should not be on raw numbers.
Conservatively, the model limitations mean that the trends shown for each scenario are likely to
underestimate the impacts of foraging and breeding habitat removal. This is despite the use of parameters
thought to be the most reasonable and accurate at the time of modelling.
Parsons Brinckerhoff | 2189220A PR_0164 ix
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
The trend shown in the modelled Scenarios 2 and 4 confirm that loss of foraging habitat in the Perth and
Peel regions will have a negative impact on the population size of Carnaby’s Cockatoo, possibly leading to
species extinction. This means that if clearing continues to occur at its current rate without effective habitat
restoration, the northern sub-population is likely to decline to extinction in less than 20 years.
Restoration attempts which include measures to improve breeding success without concomitant foraging
habitat availability will most likely fail to produce satisfactory rates of recovery.
In general, the scenarios demonstrate that reducing habitat clearance combined with minimising the gap
between the impact of any clearing and the value of restored habitat will aid the viability of this species in the
future. It is also evident that avoiding clearing of habitat early would reduce the amount of subsequent
restoration needed.
The urban consolidation scenario results in the best modelled outcome for Carnaby’s Cockatoo population
apart from the scenario showing immediate ceasing of any habitat clearing.
Another important outcome from the scenario analysis is that both foraging and breeding habitat should be
restored in tandem to gain the best improvement in population numbers.
Parsons Brinckerhoff | 2189220A PR_0164 x
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
1. Introduction
1.1
Rationale for development of a Carnaby’s Cockatoo
PVA
As part of the Australian Government’s sustainable population strategy, the Sustainable Regional
Development (SRD) program is being undertaken in selected high-growth regions across Australia.
The program will enable a more strategic approach to the management and protection of matters of national
environmental significance (MNES) in partnership with state and local governments. Regional sustainability
planning in up to seven regions will be undertaken across Australia in regional areas of high economic
growth. The Perth and Peel regions in Western Australia (Figure 1.2) comprise one of these areas of focus.
The purpose of projects being funded under the SRD program is to provide information to support the
strategic assessment of the Perth and Peel regions. The strategic assessment is being undertaken in
partnership between the Australian Government and Western Australian Government and will examine the
impacts of future urban development on MNES.
A key species potentially impacted by economic growth in the Perth and Peel regions is Carnaby’s BlackCockatoo Calyptorhynchus latirostris, an Endangered species protected under the Environment Protection
and Biodiversity Conservation Act 1999. This species is broadly distributed in south-west Western Australia
(Figure 1.1), known widely as Carnaby’s Cockatoo, and hereafter will be referred to in this document using
this localised terminology.
The population of Carnaby’s Cockatoo is estimated to have declined by approximately 50 per cent
(Garnett et al. 2010) over the last 45 years and current scientific opinion indicates that the population of the
species is continuing to decline. The population is functionally divided into a northern and a southern
subpopulation (Parsons Brinckerhoff 2013). Key threats and expected causes of this decline are: loss and
fragmentation of foraging and breeding habitat; competition for nest hollows; habitat degradation; increase in
mortality from road kill, disease, extreme weather and illegal culling; and decrease in breeding success. The
strategic assessment of the Perth and Peel regions provides an important opportunity for the conservation
issues associated with Carnaby’s Cockatoo to be analysed, and measures developed for the conservation of
the species in conjunction with the ongoing development of the region.
The continuing regional development and management actions required to conserve Carnaby’s Cockatoo
requires critical assessment and analysis, supported by the National Recovery Plan. In turn, the National
Recovery Plan indicates that research including population modelling is necessary for the conservation of the
species (Department of Environment and Conservation (DEC), 2012).
Development of a Population Viability Analysis (PVA) model will assist in the consideration of various options
for land use in relation to impacts upon the Carnaby’s Cockatoo population, and the results incorporated into
the strategic assessment. A PVA is the estimation of extinction probabilities by analyses that incorporate
identifiable threats to population survival into models of the extinction process. This PVA model is a
preliminary step in a longer process towards a fully parameterised model, and therefore is intended for
continuous refinement from this point on.
Parsons Brinckerhoff | 2189220A PR_0164 1
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
The process of preparing the PVA for Carnaby’s Cockatoo has involved three key tasks:



Task 1 – Preparation of a Carnaby’s Cockatoo literature review from published and unpublished
sources as well as incorporating expert knowledge (Parsons Brinckerhoff, 2013) (see Appendix B).
Task 2 – Preparation of peer-reviewed Population Viability Analysis model (PVA) for Carnaby’s
Cockatoo (included in this report).
Task 3 – Using information from the literature review and the PVA, identify critical life history parameters
for Carnaby’s Cockatoo, identify parameter sensitivities to data variability, and test development and
conservation scenarios in the Perth and Peel regions to provide an indication of likely trends in relation
to each scenario (included in this report).
The specific research questions discussed in this report are:

What are the critical life history parameters of Carnaby’s Cockatoo?

Which parameters are sensitive to data variations?

What is the significance of any potential loss of habitat in the Perth and Peel regions and the resulting
impact on population viability using different development and conservation scenarios?
The Literature Review in Appendix B (Parsons Brinckerhoff 2013) formed a critical part of the PVA process
and contains a review of all available background information on the ecology of Carnaby’s Cockatoo,
including available data and identified data gaps.
This PVA Model Report documents the process and results of Tasks 2 and 3.
1.2
Acknowledgements
Parsons Brinckerhoff wishes to acknowledge the contribution of Erin Pears (Acting Assistant Director –
Strategic Approaches: Department of Sustainability, Environment, Water, Population and Communities),
Professor Michael Mahony (University of Newcastle) and Ron Johnstone (Curator, Ornithology, Terrestrial
Vertebrates, Western Australian Museum) in providing comments on the draft PVA report. Thanks go to the
contributing team in the Department for their continued valuable input into the project.
Thanks also go to members of the Carnaby’s Cockatoo Recovery Team and to all attendees at the Expert
Workshop conducted as part of the literature review and related PVA process for their valuable input and
continued assistance. A list of attendees is provided in the literature review (Parsons Brinckerhoff 2013) in
Appendix B.
Parsons Brinckerhoff | 2189220A PR_0164 2
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
This page should be replaced with the corresponding GIS figure once the
document has been pdf'd. This caption page must follow an even numbered page
if the figure is A3 size or larger.
Figure 1.1
Recorded distribution of Carnaby’s Cockatoo
Parsons Brinckerhoff | 2189220A PR_0164 3
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
This page should be replaced with the corresponding GIS figure once the
document has been pdf'd. This caption page must follow an even numbered page
if the figure is A3 size or larger.
Figure 1.2
Location of Perth and Peel regions
Parsons Brinckerhoff | 2189220A PR_0164 4
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
2. Methodology
2.1
Personnel
The contributors to the preparation of this study, their qualifications and roles are listed in Table 2.1.
Table 2.1
Study team
Name
Qualifications
Position and role
Alex Cockerill
BSc (Hons)
Project Director – report review
Toby Lambert
BEnvSc
Project Manager – report preparation and review
Lawrie Conole
Grad Cert Ornithology,
PhD candidate
PVA manager and report preparation
Evan Pickett
BSc (Hons), PhD
PVA modeller and report preparation, Newcastle
Innovation (University of Newcastle)
Michael Mahony
BA (Biology), PhD
PVA and report review, Newcastle Innovation (University of
Newcastle)
Ron Johnstone
–
PVA and report review, Western Australia Museum
Sam Wilkins
Dip GIS
GIS team lead
Selga Harrington
BSc (Hons)
Report review
Rob Suansri
BSc
GIS specialist
2.2
Literature review
A detailed literature review was undertaken to inform the development of the PVA (Parsons Brinckerhoff,
2013). Current knowledge of the Carnaby’s Cockatoo was reviewed with particular focus on population
dynamics and causes of decline. The literature review is provided in Appendix B for detailed background
purposes.
2.3
Modelling approach
Initially, use of the open source R statistical framework (R Development Core Team 2013) was considered
as the preferred model platform. Upon further consideration the VORTEX (Lacy et al. 2013) software
package for PVA was determined to be suitable for the reasons summarised below (see also Table 2.2):

Using a series of ‘packages’ within R would provide the most flexible platform for the PVA, but the
flexibility is accompanied by a very steep learning curve. The approach for using R requires
programming experience and expertise.

R would allow great adaptability in the event that the life history characteristics of the subject were
complex or unusual, but Carnaby’s Cockatoo has a fairly straightforward life history, thus negating one
of R’s chief advantages.

Although R is widely used, so too is VORTEX and to a lesser extent RAMAS (Akçakaya 2002).
VORTEX is the most widely deployed PVA platform available (Brook et al. 2000).
Parsons Brinckerhoff | 2189220A PR_0164 5
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report

RAMAS is more closely coupled with the MAXENT process of niche modelling and less suited to the
straight PVA that is the object of the Carnaby’s Cockatoo project. RAMAS is also commercial, not
freeware or open source.

Both R and VORTEX are freeware (R is also open source).

VORTEX’s graphical user interface makes it simpler to use for non-programmers and likely makes it
more suitable for future use and development by third parties.
Table 2.2
Summary table for comparison of PVA platforms
Consideration
VORTEX
RAMAS
R
Interface
Graphical user-friendly
interface
Graphical user-friendly
interface/GIS
Script-based coding interface
Cost/Availability
Freeware
Commercial
Freeware
Designed for
Populations and
metapopulation
dynamics
Spatial demography and
metapopulation dynamics
Flexible (difficulty of use
increases with more complex
designs)
Difficulty of adaptation
without previous experience
Relatively simple
Computer coding
experience
Relatively simple for
demography
Demographic parameters
relatively simple
More difficult for spatial
analysis
Model design very difficult
None required
None required
Required
Citations in literature*
439
237
384
Sensitivity Analysis
Yes
Yes
Yes
Stochastic Analysis
Yes
Yes
Yes
Parametric Uncertainty
No
No
Yes
Biologically suitable for
Carnaby’s Cockatoo?
Yes
Yes
Yes
*Number of citations recorded by Google Scholar for the original scientific paper describing the software. This is used
as a rough guide to its uptake within the field of conservation biology. R citations were refined using the term
‘population viability’ as it is cited widely for other statistical purposes.
Having considered the above matters, VORTEX was considered the most sensible choice and offered PVA
accuracy, customisability and ease of use with ready transferability to other users.
VORTEX is an individual-based simulation model for PVA and is the most widely deployed PVA platform
available (Brook et al., 2000). VORTEX models population dynamics as discrete, sequential events
(e.g., births, deaths, etc.) that occur according to defined probabilities (Miller & Lacy, 2005). The model is
repeated to reveal the distribution of fates that the population might experience under a given set of input
conditions (Miller & Lacy, 2005).
Parsons Brinckerhoff | 2189220A PR_0164 6
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
2.4
Population biology parameters
Drawing on the data gathered during the literature review (Parsons Brinckerhoff, 2013), the expert workshop
in Perth (April 2013), data made available from Warren et al. (2013 in prep.), and data analysis, a list of PVA
input parameters were developed.
The list of parameters assembled in the literature review (Parsons Brinckerhoff 2013) have been further
refined and expanded as part of the modelling workup, and are presented below (Table 2.3).
Table 2.3
PVA parameters used in development of the PVA models
Variable
Value
Source
Age of 1st reproduction for females
4 years
Saunders (1982, 1986)
Age of 1st reproduction for males
4 years
Saunders (1982, 1986)
Maximum breeding age
60
Jupp (1996)
Sex ratio at birth
0.5
Saunders (1982)
Mating system
Long-term monogamous
Higgins (1999)
Adult males in breeding pool
100
Assumption made for modelling
purposes.
Adult females breeding
Density dependent1
Assumption made for modelling
purposes
Environmental Variation in % female
adults breeding
0
Assumption made for modelling
purposes
Females producing 0 broods
Based on above
Assumption made for modelling
purposes
Females producing 1 brood
1002
Estimated from data
Mean No. of offspring /female/year
1.56
Saunders (1982), Smith and
Saunders (1986)
Standard Deviation (SD) in No. of
offspring
1
Estimated from data as no SD
was provided in source data
(above)
Initial population size (adults)
20,000 each
Mawson and Johnstone (1997)
(50:50 north:south)
Carrying capacity
20,000 each sub-population
Assumption made for modelling
purposes
Dispersal
10%
Based on ‘small level of
migration’ (not quantified)
1
Based on an arbitrary estimate that 10–30% of the population could breed during the breeding season.
2
All females that could breed (based on % adults females breeding) were allowed to breed and then were impacted by egg survival.
Parsons Brinckerhoff | 2189220A PR_0164 7
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
2.5
Test group and peer review of PVA
Following the preparation of the literature review and identification of parameters for use in the PVA model, a
test group meeting was organised on 22 May 2012. Attendees at the test group meeting were a subset of the
experts who attended the expert workshop that occurred as part of the literature review process
(see Appendix B), plus additional Department of Environment and Conservation (DEC) personnel.
In attendance at the test group meeting were:

Nicole Matthews, SEWPaC.

Erin Pears, SEWPaC.

Toby Lambert, Parsons Brinckerhoff.

Lawrie Conole, Parsons Brinckerhoff.

David Mitchell, DEC.

Rick Dawson, DEC.

Colin Yates, DEC.

Carly Bishop, DEC.

Hugh Finn, Murdoch University.

Will Stock, Edith Cowan University.
The purpose of the workshop was to gain feedback on the preliminary PVA model and receive input to allow
further refinement of the PVA model where necessary.
A separate meeting was also held on 22 May 2012 to discuss the scenarios modelled in this report from a
strategic planning perspective. Attendees at the meeting were:

Nicole Matthews, SEWPaC.

Erin Pears, SEWPaC.

Toby Lambert, Parsons Brinckerhoff.

Lawrie Conole, Parsons Brinckerhoff.

David Mitchell, DEC.

Bryce Bunny, Department of Planning.

Catherine Garlick, Office of Environmental Protection Authority.

Claire Cummings, Department of Premier and Cabinet.
Peer review of the PVA model and this document was undertaken separately by:

Ron Johnstone, Western Australia Museum.

Michael Mahony, Newcastle Innovation (University of Newcastle).
Thanks go to all participants in the PVA modelling and reporting process for their generous time and input.
Parsons Brinckerhoff | 2189220A PR_0164 8
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
2.6
Assumptions of the PVA model
2.6.1
Overview
A number of the parameters presented in Table 2.3 are well supported by research and experimental data.
Estimates of the age of first breeding, sex ratio at birth, mating system, females producing one brood, and
mean number of offspring for females per year are sourced directly from the research literature
(Parsons Brinckerhoff, 2013).
Other parameters have a degree of uncertainty associated with them as a consequence of, in most cases,
there being no evidence-based firm estimates. It is considered that this is an important limitation of the
current modelling process that should be noted by end-users.
The total population size for Carnaby’s Cockatoo and that of the two major sub-populations are based on
expert opinion and summarised in the literature review (Parsons Brinckerhoff, 2013). It should be noted that
these are only estimates and may be substantially revised after further research is completed. A total of
30,000 was used in constructing the initial model due to the tendency for the trend to rapid extinction in
VORTEX using lower numbers. As this PVA is being used to examine trends rather than fixed numbers, this
approach is regarded as defensible and reliable.
Carnaby’s Cockatoo does not breed until at least four years of age (Saunders 1982, 1986). This is a
relatively late onset of sexual maturity, and the bird is therefore likely to be long-lived as life history analyses
in birds suggest an association between slow maturity and a long life span (Holmes & Austad 1995;
de Magalhães, Costa & Church 2007). The maximum age reached by Carnaby’s Cockatoo is not known, and
the figure used here is a speculative maximum (Jupp, 1996) which is almost twice the age of the oldest
documented age (34.4 years) for a banded bird (Saunders & Dawson, 2009). Data on maximum annual
survival of post-fledging birds comes from three sources (Saunders, 1982; Mooney & Pedler, 2005;
Warren et al., 2013 in prep.).
A more detailed discussion of the estimation of particular model parameters follows.
2.6.2
Estimates of post-fledging mortality rates
Mortality during the first year of life includes three distinct life-history stages: eggs, hatchling and postfledging. Egg survival was estimated from Saunders (1982) using the proportion of failed and hatched eggs.
The fledging mortality rate from Saunders (1982) was similarly used for the period between hatching and
fledging and the post-fledging survival rates determined below were used for the rest of the annual survival.
These mortalities were combined to produce a single estimate for the first year.
Post-fledging is considered to be the period after young birds mature from the nestling stage, and in the field
quickly become indistinguishable from adults. Post-fledging survival is equivalent to adult survival except in
other bird species where a distinct immature plumaged stage exists.
Three estimates of post-fledging mortality rate were tested (see sections 2.6.1.1–2.6.1.3 below).
2.6.2.1
Return rate
Data from Saunders (1982) produced a ‘return rate’ between years of 60.6–69.0% for birds at two sites in the
northern population that corresponds to a minimum survival rate. The return rate overestimates post-fledging
mortality because it takes no account of detectability of birds in subsequent seasons. That is, if birds do not
return to the same site to breed in later years, they disappear from the return rate data but are not
necessarily dead. Arithmetically, such a high annual mortality (up to approximately a third of post-fledging
birds) is likely to lead to extinction of the population in as little as a decade (Evan Pickett, pers. comm.,
Parsons Brinckerhoff | 2189220A PR_0164 9
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
April 2013). Given the demographic limitations of return rates, it is therefore unlikely that they constitute
adequate proxies for annual adult survival.
2.6.2.2
Age-structure of heatwave birds
A second estimate was based on the mortality rates derived from the age-structure of dead birds found at
Hopetoun and Munglinup after an intense heatwave (Warren et al., 2013 in prep.). The regression of age
structure data technique was used for determining survival from an age distribution (Skalski et al., 2005)
(Figure 2.1) for a survival estimate of 95.2%, with the following assumptions:

Each cockatoo age was rounded to the nearest whole number and each age was considered an age
class. The log of the frequency of an age class was correlated to age to produce the following
regression formula.
ln(lx) = 1.773456 – 0.048401(Age)

The exponential of the linear component was considered the survival rate.
e(-0.048401) = 0.9527521

Standard error was determined using the following equation.
SE = Surv2*Var(B)

Where Var(B) is the variance of the linear component of the above regression and Surv is the above
estimated survival rate.
Figure 2.1
Regression of age structure data technique for determining survival from an age distribution
(Skalski et al. 2005)
Source data from Hopetoun and Munglinup (Warren et al, 2013 in prep).
Parsons Brinckerhoff | 2189220A PR_0164 10
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
The survival rate of 95.2% derived from the Hopetoun-Munglinup data (Warren et al., 2013 in prep.) is
notably higher than the ‘return rate’ of 60.6–69% produced from Saunders (1982) data, but is similar to the
maximum survival rate posited for the Kangaroo Island Glossy Black-Cockatoo (Glossy Black-Cockatoo
Recovery Program, unpublished data; L. Pedler 2007, pers. comm.). A bootstrap resampled estimate (Canty
& Ripley 2012) of age distribution from the sample of 96 aged birds (Warren et al., 2013 in prep.) showed
that the 95% confidence intervals for that group were in the range 9.37–13.04 years (Figure 2.2), with only
five (5.2%) birds greater than 30 years of age.
Figure 2.2
Distribution of age classes in Carnaby’s Cockatoo (100,000 bootstrap iterations)
Source data from Hopetoun and Munglinup (Warren et al., 2013 in prep.). The 95% confidence intervals are
9.37–13.04 years.
The expert group that met in Perth on 22 May 2013, suggested that the age structure of the HopetounMunglinup flock is unlikely to be representative of the Carnaby’s Cockatoo population in total. The HopetounMunglinup population is regarded as likely to be either a recently established population subject to founder
effects (Ron Johnstone, pers. comm., May 2013) or a sink population (Will Stock, pers. comm., May 2013).
In either case it is reasonable to assume that the age structure of the entire Carnaby’s Cockatoo population
may differ from the Hopetoun-Munglinup sample.
2.6.2.3
Proxy data from Glossy Black-Cockatoo PVA
Despite these issues, due to the absence of any similar age structure data from elsewhere in the range of
Carnaby’s Cockatoo, a decision was made to use these data in defining an upper bound (95.2%) to the
survival rate for the species, and to utilise Saunders (1982) return rates as the lower bound (60.6%). For this
Carnaby’s Cockatoo PVA a survival rate of 90% was tested, based on the data-derived figure used for the
Glossy Black-Cockatoo PVA (Mooney & Pedler, 2005), and lying between the upper and lower bounds
discussed above.
Parsons Brinckerhoff | 2189220A PR_0164 11
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
2.6.2.4
Summary
The survival rate for the first year is the product of egg, hatchling and post-fledging survival whilst the
survival rate for birds over one year of age was the post-fledging survival rate.
Maximum mortality was derived from return rates of cockatoos to breeding area in the northern subpopulation at Coomallo Creek and Manmanning (Saunders 1982). Mortality from age-structure was derived
from age distribution data from dead birds in the southern population at Munglinup and Hopetoun
(Warren et al. 2013 in prep.). An annual survival rate of 90% was based on the possible positive bias in agestructure data, and reflects the data used in the Glossy Black-Cockatoo PVA (Mooney and Pedler 2005).
See Figure 2.3.
Figure 2.3
Impact of different mortality regimes on projected population of Carnaby’s Cockatoo. Y-axis
represents proportion of the initial population size.
Red line (lower) shows trajectory based on return rate data (Saunders 1982). Blue line (top)
shows trajectory based on derived mortality figure from Warren et al. (in prep 2013) data. Green
line (middle) shows trajectory based on Mooney & Pedler (2005) data for Kangaroo Island
Glossy Black-Cockatoo.
2.6.3
Estimation of reproductive rates
Reproductive rates are relatively well-known for Carnaby’s Cockatoo. However, the maximum number of
birds that can breed during a particular year is not known and the current model was based on the
assumption that the population is heavily influenced by reproductive density dependence.
Sensitivity analysis of three values (30%, 16% and 10%) for the proportion of Carnaby’s Cockatoo pairs that
can breed during a particular year were used (Figure 2.4), following feedback from the test group. The 10–
16% value is based on the available data for the proportion of Forest Red-tailed Black Cockatoos
(Calyptorhynchus banksii naso) that are believed to breed during a particular year (Johnstone & Kirkby,
2005). The Forest Red-tailed Black Cockatoo is considered to be the most similar species for which this data
exists. The figure of 30% represents an upper bound based on opinion of the PVA team for sensitivity testing
alone.
Parsons Brinckerhoff | 2189220A PR_0164 12
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
These values are modelled on the reproductive capacity of the population at the initial carrying capacity.
Models were developed so that the proportion of reproductive pairs would be inversely related to population
size. In other words, as the size of the population decreases, the same number of birds (but by definition a
larger proportion) can breed if the availability of viable nest sites remains the same. This means that
approximately the same numbers of animals breed until the population size reduces below the number of
available breeding hollows, after which breeding numbers would decline. The model assumes that the
breeding rate does not change with age due to the lack of ageing data for Carnaby’s Cockatoo. It also
assumes that the chance of breeding is identical for every mature bird, with no individual heterogeneity built
into the model.
The model was heavily influenced by this factor at high population size; therefore this requires study and
refinement, as a decrease in breeding capacity will have major negative impacts on the carrying capacity of
the population and therefore the overall population size.
2.6.4
Sensitivity analysis
The sensitivity analysis is a study of how predictable a model is (e.g. PVA) by measuring the reliability of the
data sets used to generate the model.
As expected for a low fecundity species, sensitivity analysis of the ‘return rates’ from Saunders (1982) as a
mortality estimate produced a scenario where the population declined rapidly to extinction (Figure 2.3).
Sensitivity analysis of the age-distribution data scenario based on heat wave mortality birds (Warren et al.
2013 in prep.) maintained a population very close to the carrying capacity (Figure 2.3), suggesting that
Carnaby’s Cockatoo population dynamics are highly reliant on limiting resources such as food availability
and breeding hollows. However, short survey times and the survey methods excluding rare stochastic events
(such as disease or heatwaves) were likely to overestimate this parameter.
Sensitivity analysis using the 90% survival scenario maintained a stable population without maintaining a
close association with the carrying capacity (Figure 2.3). This scenario was used for sensitivity analyses of
other parameters as positive impacts would be undetectable using a model which ran at the carrying
capacity.
This is modelled in VORTEX by altering the ‘% Adult females breeding’ in the ‘Reproductive Rates’ section to
the following equation:
= (100-((100-16)*((N/30000)^1)))
Where 16 is the percentage of females breeding at the model carrying capacity of 30,000.
The initial drop in each of the trajectories (Figure 2.4) is as a consequence of breeding carrying capacity
having an effect on the population. It causes the population to run below carrying capacity and as the initial
population size was set at 30,000 to satisfy VORTEX requirements, it results in an initial drop in the
population.
Parsons Brinckerhoff | 2189220A PR_0164 13
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Figure 2.4
Sensitivity testing of Scenario 1 with three estimates of the proportion of Carnaby’s Cockatoo
pairs that can breed in a given year (10%, 16% and 30%). Y-axis represents proportion of the
initial population size.
2.6.5
PVA model runs of carrying capacity and population size
Different scenarios were run to test the impact of different population sizes, carrying capacities and
reproductive carrying capacities. For both initial population sizes (N= 5,000; 10,000 for both subpopulations
combined – these numbers selected for computer run time efficiency), the population would maintain at a
stable size depending on the carrying capacity system (see below), except the ‘return rate’ mortality scenario
which rapidly trended to extinction (Figure 2.5). This high dependence on carrying capacity is typical for longlived populations such as Carnaby’s Cockatoo. It is therefore expected that scenarios which alter the
carrying capacity will have a significant impact on this population. Such scenarios include:

removal of food resources

removal of breeding hollows.
Scenarios with a reproductive carrying capacity which represented a limited number of breeding hollows,
stabilised at a population size below the carrying capacity after approximately 20 years (Figure 2.5).
This time lag would mean that the population will decline for a period of time after destruction of breeding
hollows but can stabilise if nest hollow abundance (and other parameters) subsequently remains unchanged.
The reproductive carrying capacity indicates it could take approximately 20 years for a population to stabilise
after a decline of breeding habitat (Figure 2.5). This is important to note as it means that the existing
population is likely to be in such a period of stabilisation, although not enough data is available on this to
include impacts of time lag on the model.
The current population models do not include mass mortality (stochastic) events as they have not been
quantified (data on the frequency and intensity of these events is required). Evidence of these events exists
(e.g. disease outbreak and heat waves) but the impact of such events cannot be known until these data are
collected and analysed.
Parsons Brinckerhoff | 2189220A PR_0164 14
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Figure 2.5
Comparison of scenarios with different starting populations/carrying capacity (Pop) and
breeding systems. Y-axis represents proportion of the initial population size.
‘All breeding’ is where 100% of the females can breed. Reproductive carrying capacity means that at
high density, only a proportion (30%) can breed each year.
Vegetation clearing reduced the carrying capacity of the population, as would be expected 15,000 hectares
of pine can support 9,280 Carnaby’s Cockatoos for six months (Stock et al., 2013), and therefore a hectare
of pine can support 0.6187 birds. This ratio was used to determine the maximum possible reduction in
carrying capacity for each scenario where vegetation was cleared. For example, the clearance of 15,000
hectares of pines would result in a reduction in carrying capacity of approximately 62%. A similar calculation
can be run for native vegetation of lower carrying capacity.
2.6.6
Population
For the development scenarios, an initial population size and carrying capacity of 30,000 birds was used.
Parsons Brinckerhoff (2013) outlines that there is a high degree of uncertainty in relation to the likely existing
total extant population, and that estimates vary between 11,000 and 60,000. The precise population number
for the northern subpopulation of Carnaby’s Cockatoo is unknown however 30,000 was chosen as the
maximum impact would reduce the population to a low number but not induce extinction unless the
population is unstable at low sizes.
It is possible that the current population is experiencing decline due to past habitat loss which reduced
carrying capacity. Importantly if this is the case, the population trajectories from further clearing scenarios will
have a larger effect than is currently predicted.
Management of Carnaby’s Cockatoo should seek to prevent actions that decrease the population to a small
size. Small populations are at increased risk of stochastic extinction and inbreeding depression. This can
result in rapid extinction once inbreeding impacts vital rates (e.g. Madsen et al. 1996). Two recent studies
independently estimated minimum viable population (MVP) size for many species, and median MVPs of
5816 and 4169 breeding adults respectively (Reed et al. 2003; Traill et al. 2007).
Parsons Brinckerhoff | 2189220A PR_0164 15
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Changes in carrying capacity in VORTEX are modelled as a per year percentage decrease over a certain
time-period. Vegetation clearing was to occur over 20 years; therefore the reduction was split over these
years. This was achieved by determining the proportion decrease:
62% ÷ 20 = 3.1%/𝑦𝑟
An equivalent calculation was run for native vegetation of lower carrying capacity using a birds/hectare
support figure of 2.4 to take into account a 1:4 calorific ratio between native vegetation and pine as identified
by Stock et al (2013).
The same method was used for increasing from habitat improvement (gain) post-decline where the
population size post-decline was used as the initial population size and carrying capacity and the percentage
increase over 20 years of vegetation succession was modelled as the increase in carrying capacity.
Habitat improvement (gain) that increased the potential breeding sites for Carnaby’s Cockatoo was also
modelled. The linear component of the reproductive rate for percentage of adult females breeding was
altered so that the carrying capacity was increased by the percentage indicated for breeding improvement.
For example, an increase of 10% to the carrying capacity of 30,000 results in a new reproductive carrying
capacity of 33,000. Therefore, in this example, the modelled reproductive carrying capacity was altered to:
= (100-((100-30)*((N/33000)^1)))
The modelled scenarios are outlined in further detail below.
Parsons Brinckerhoff | 2189220A PR_0164 16
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
3. Modelled scenarios
Scenarios with different indicative levels of vegetation clearing and habitat restoration (gain) were modelled
to provide an indication of population trends where hypothetical impacts occur within the Perth and Peel
regions and surrounds. These scenarios affected two primary parameters associated with the carrying
capacity of the population.
The set of six development and conservation scenarios were developed by SEWPaC, and then refined
during workshops on 22 May 2013 in Perth with representatives of SEWPaC, the consultant (Parsons
Brinckerhoff), the WA Department of Environment and Conservation, WA Department of Premier and
Cabinet, WA Environment Protection Agency, and WA Department of Planning. A summary of these
scenarios is presented below.
It is very important to note that, while based on real time considerations, these are hypothetical scenarios
designed to demonstrate the relative magnitude of differences between different potential approaches and
the impacts of these on Carnaby’s Cockatoo.
3.1
Scenario summary
A summary of each modelled scenario is provided below and in Appendix A. The technical values used in
the translation of scenarios to model parameters is summarised in Table 3.1. This information is presented
for reference to assist any potential future updates or modifications of the PVA model.
Table 3.1
Conversion of hypothetical development scenarios to PVA parameters
Scenario
Parameter
Value
1
No change
NA
Future change in carrying capacity:
2
3
4
Years
20 years
Annual change
-4.1245%
Initial population size
3,000
Future change in carrying capacity:
Years
15 years
Annual change
354%
Initial population size
3,000
% Adult females breeding
= (100-((100-30)*((N/48000)^1)))
Initial population size
9,000
Future change in carrying capacity:
5
Years
15 years
Annual change
38.9%
% Adult females breeding
= (100-((100-30)*((N/34500)^1)))
Initial population size
15,000
Future change in carrying capacity:
6
Years
15
Annual change
16.5%
% Adult females breeding
= (100-((100-30)*((N/33000)^1)))
Parsons Brinckerhoff | 2189220A PR_0164 17
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
3.1.1
Scenario 1
This scenario assumes no further clearing of Carnaby’s Cockatoo habitat, and there are no further impacts
and no improvements or habitat restoration (gain). The objective of this scenario is to understand the
hypothetical impacts upon Carnaby’s Cockatoo if clearing of habitats were to cease immediately, and
existing habitats were protected but not enhanced.
3.1.2
Scenario 2
This is the ‘do nothing’ or ‘worst case’ scenario, where development is undertaken with no consideration of
‘avoid, mitigate and habitat restoration’ three-step process. The objective of this scenario is to understand
the hypothetical impacts upon Carnaby’s Cockatoo if clearing of habitats were not to cease immediately and
were not offset by habitat restoration.
3.1.3
Scenario 3
This scenario expects that all potential impacts on Carnaby’s Cockatoo in the Perth and Peel regions would
be assessed on a case-by-case basis. Removal of habitat for urban development, basic raw material
extraction and non-replacement of pine plantations would continue as they currently exist. The habitat
improvement (which may include creating new habitat or improvement in quality of existing habitat, or a
combination) figures are based on estimates of in situ offsets provided for projects since implementation of
the EPBC Act offset policy. It is assumed that some other compensatory measures would go towards
improvement of breeding habitat.
3.1.4
Scenario 4
In this scenario, improving breeding success is the sole conservation response, but there is still a loss of
foraging habitat. Improving breeding success would be targeted by direct measures such as maintenance of
hollows, installation of artificial hollows and management of pests (e.g. bees). The objective is to understand
the impact if all conservation effort is focussed on breeding success, but there is loss of foraging habitat. This
assists in determining how effective implementation of direct breeding assistance measures would be without
also having enough foraging habitat or restoration of foraging habitat occurring at the same time.
3.1.5
Scenario 5
This scenario is the potential theoretical urban development scenario, assuming some urban development
will occur accompanied by some avoidance and mitigation and a portion of pine plantations is to be retained.
The objective of this scenario is to understand the impact of a hypothetical area to be cleared for urban
development in the Perth and Peel regions (after avoid and mitigate is implemented) in combination with
potential restoration of foraging and breeding habitat being implemented.
3.1.6
Scenario 6
The consolidated urban development scenario assumes that extent of clearing is reduced using consolidated
urban form, partial retention of pine plantations and avoidance of basic raw material extraction (through
reduction in demand). The objective of this scenario is to assess the hypothetical impact if the area of
clearing used in Scenario 5 is reduced by using consolidated urban form, partial retention of pine plantations
and avoidance of basic raw material extraction (through reduction in demand).
Parsons Brinckerhoff | 2189220A PR_0164 18
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
3.2
Scenario assumptions
The following assumptions have been made for the scenarios presented in Appendix A, as provided by
SEWPaC for assessment in the model:

In relation to the SEWPaC offset guide, that quality of habitat removed for urban development is
assumed to be equivalent in quality to habitat restored.

Breeding habitat improvement is measured in terms of the improvement in recruitment.

Temporal aspects of impacts were built into scenarios by calculating rates of change.

Current population size occurs close to both foraging and reproductive carrying capacity.
3.3
Simulated population trajectories
The range of Carnaby’s Cockatoo is estimated to have contracted by greater than 30% since the late 1940s
(Mawson and Johnstone 1997), and the species is regarded as having disappeared from more than 33% of
its former breeding range between 1968 and 1990 (Saunders and Ingram 1998), coincident with the
estimated reduction in population size. A reduction in the number of Carnaby’s Cockatoos visiting the Perth
and Peel regions has been estimated from roost counts (the ‘Great Cocky Count’, Kabat et al. 2012), but the
relationship with any current rate of decline of the species is not clear.
It is important to note that it is possible, in fact likely, that the current population is continuing to experience
decline due to past habitat degradation which in turn has reduced carrying capacity. If this is the case, the
population trajectories from further clearing scenarios will have a larger effect than is predicted by the
outputs of this current PVA model. This is a critical point as it means that even the trends predicted in the
model should be considered as best case.
The decline (Scenario 1 and 2) and recovery models (Scenarios 3–6) are run separately and sequentially
rather than in combination, as they are pulling the model in opposing directions and cannot be run
simultaneously (Figures 3.1 and 3.2).
In addition to this historical background, substantial declines in the population of the Carnaby’s Cockatoo are
expected under all scenarios that involve native vegetation removal, whereby an initial theoretical population
could be reduced by up to approximately 80% over a period of five years (Figures 3.1 and 3.2).
The impact of habitat restoration scenarios is assumed to start from the population low points induced by the
initial habitat loss (Figure 3.2). The different scenarios have different levels of clearing and therefore the
population has declined to differing extents in each scenario, and each simulated population trajectory starts
from a different position.
Scenario 4 involves offsets of improving breeding success but no re-establishment of foraging habitat, and
the PVA predicts this approach will not contribute to Carnaby’s Cockatoo recovery, whereas Scenarios 3, 5
and 6 which combine varying degrees of habitat re-establishment with attempts to improve breeding success
are modelled as being more likely to bring about Carnaby’s Cockatoo population recovery within 30 years
(Figure 3.2).
Parsons Brinckerhoff | 2189220A PR_0164 19
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
Figure 3.1
Mean expected population sizes for the Carnaby’s Cockatoo under the first two (Scenario 1,
Scenario 2) of six management scenarios. Y-axis represents proportion of the initial
population size.
Both are ‘no offset/restoration’ scenarios, but Scenario 1 involves no clearing, whilst Scenario 2 involves
clearing of 43,000 ha of habitat. The rate of decline varies because the rate of clearing varies between the
scenarios.
Figure 3.2
Mean expected population sizes for the Carnaby’s Cockatoo under four (Scenario 3, Scenario
4, Scenario 5 and Scenario 6) of six management scenarios. Y-axis represents proportion of
the initial population size.
Parsons Brinckerhoff | 2189220A PR_0164 20
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
4. Discussion
4.1
Scenario analysis
4.1.1
Uncertainty
The scenarios outlined and modelled in Section 3 only provide a general indication of trends for each of the
hypothetical scenarios. The greatest value of undertaking a PVA is for this reason, however due to the
complex interaction of PVA parameters of varying reliability, focus should not be on raw numbers.
Although the PVA and scenarios tested have been developed based on the most current and relevant
scientific literature available for Carnaby’s Cockatoo, it is importantly acknowledged that there are still many
uncertainties in the understanding of Carnaby’s Cockatoo ecology.
Complicating factors that apply to the current PVA model that cannot be resolved until further research is
undertaken include:


There is likely to be a time lag between the removal of foraging and breeding habitat that has already
occurred and the true population or carrying capacity at the present time.
An accurate population figure for Carnaby’s Cockatoo is not known and estimates vary widely. The
lower the actual population the more likely that it will be susceptible to interbreeding and genetic
weakness.

Stochastic events have not been included and cannot be included until further research is undertaken.

It is assumed that restored habitat is equivalent to existing good quality habitat for the species. In reality
this is difficult to achieve without substantive effort and expenditure.

The scenarios assess habitat removal within the Perth and Peel regions and surrounds. Additional
habitat clearing occurs across the modelled distribution of the species.
Conservatively, such limitations mean that the trends shown for each scenario are likely to underestimate the
impacts of foraging and breeding habitat removal. This is despite the use of parameters thought to be the
most reasonable and accurate at the time of modelling.
As such, the trends shown in the scenarios should only be used as a general guide for strategic conservation
planning for the species. The accuracy of the PVA model could be increased as new research becomes
available in the future, if desired.
4.1.2
Scenario 1
This scenario assesses the hypothetical impacts upon Carnaby’s Cockatoo if clearing of habitats were to
cease immediately, and existing habitats were protected but not enhanced. The trend in Figure 3.1 clearly
shows that the existing population remains at relatively stable numbers. This is to be expected for this
scenario and provides a baseline trend against which to compare the other five scenarios. In reality though
as previously discussed, the unaccounted–for lag time between habitat removal and population stabilising
means that even if clearing ceased immediately, the population is still likely to decline for a period due to the
long-lived nature of the species. To what degree, or over which period, this would occur is not known.
Parsons Brinckerhoff | 2189220A PR_0164 21
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
4.1.3
Scenario 2
The objective of this scenario is to understand the hypothetical impacts upon Carnaby’s Cockatoo if clearing
of habitats were not to cease immediately and were not offset by habitat restoration.
The overall trend shown for this scenario indicates a sustained reduction in the population size over the
20 year period in which clearing of habitat is expected to occur in the Perth and Peel regions. As mentioned
previously clearing of habitats is also likely to occur in other areas, further exacerbating this trend. The clear
trend of this scenario that shows the existing situation is a trending towards species extinction. It is not
clearly known at what point the population would become unviable such that extinction in inevitable.
However if it is assumed that the current northern sub-population is approximately 20,000, being half the
total 40,000 population estimated by Garnett et al. (2010), then the trend of population decline would result in
a decline to around 2,000 individuals in 20 years. As mentioned previously in this report small populations
are at increased risk of stochastic extinction and inbreeding depression. This can result in rapid extinction
once inbreeding impacts vital rates (e.g. Madsen et al. 1996). This is a lower number than the minimum
viable population of 5816 and 4169 breeding adults outlined by Reed et al. (2003) and Traill et al. (2007)
respectively. While significant caution needs to be applied to this interpretation, nevertheless a general trend
towards extinction of the northern sub-population in 20 years if clearing occurred without adequate
conservation response is considered likely.
Given the likely underestimation of the trend by the PVA model, it is likely that there is substantially less time
available to address species decline than otherwise might be indicated by the modelled scenario. An
accurate prediction cannot be made in this regard.
4.1.4
Scenario 3
This scenario assumes that removal of habitat for urban development, basic raw material extraction and nonreplacement of pine plantations would continue to occur as in Scenario 2. However habitat
creation/restoration would also occur, for which the values used are based on estimates of in situ offsets
provided for projects since implementation of the EPBC Act offset policy.
The modelling of this scenario shows a slow recovery over a period of around 25 years to what is likely to be
a relatively stable population. This assumes restoration of vast areas of both native and pine habitats to a
condition similar to existing good quality habitat.
Whilst it could appear that this scenario is viable, the major issue is that the population could already have
declined to numbers that are unlikely to be viable, so extinction may have occurred by the starting point of
the predicted recovery. Genetic integrity of the base population is also likely to have been compromised.
Nevertheless the model predicts that, if a small viable population does persist, a substantial recovery would
occur over the 25 year period. A minimum period of 25 years for recovery is likely particularly given the low
fecundity of the species.
4.1.5
Scenario 4
The objective for this scenario is to understand the impact if all conservation effort is focussed on breeding
success, but there is loss of foraging habitat.
This scenario shows that the species could not recover based on improvement of breeding habitat alone. In
this instance the availability of foraging habitat would be the limiting factor for the carrying capacity.
While the model indicates that a small population would persist over the 25 years, the likelihood is that this
species would become extinct over this time due to either inbreeding or a stochastic event.
Parsons Brinckerhoff | 2189220A PR_0164 22
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
This scenario also shows that investing in breeding habitat (primarily hollows) without investing in foraging
habitat at the same time is likely to be ineffective.
4.1.6
Scenario 5
The objective of this scenario is to understand the impact of a hypothetical area to be cleared for urban
development in the Perth and Peel regions (after avoid and mitigate is implemented) in combination with
potential restoration of foraging and breeding habitat being implemented.
The relative population size is starting from a higher base point for this scenario due to the implementation of
the concept of avoidance of more existing habitat from clearing. This means that the species is more likely to
be able to recover more quickly to a stable viable population than in Scenarios 3 and 4 as it will not have
reduced to the threshold considered to result in viability uncertainty.
The trend shown shows an increase in the population to pre-clearing levels over a period of around 20 years.
This assumes substantial investment occurs in foraging and breeding habitat restoration in association with
existing habitat conservation.
4.1.7
Scenario 6
The objective of this scenario is to assess the hypothetical impact if the area of clearing used in scenario 5 is
reduced by using consolidated urban form, partial retention of pine plantations and avoidance of basic raw
material extraction (through reduction in demand).
The apparent difference in Figure 3.1 between Scenario 5 and this scenario is that again this scenario starts
from an even higher base point than Scenario 5 because more of the existing habitat has been avoided and
conserved. This shows that the species can more easily recover if foraging and breeding habitat are
restored.
Of all the scenarios, this consolidated urban form scenario appears to provide the best outcome for the
population apart from Scenario 1.
4.2
Research questions
The specific research questions for this report are discussed below, namely:

What are the critical life history parameters of Carnaby’s Cockatoo?

Which parameters are sensitive to data variations?

What is the significance of any potential loss of habitat in the Perth and Peel regions and the resulting
impact on population viability using different development and conservation scenarios?
Though the PVA and scenarios have been developed based on the most current and relevant scientific
literature available for Carnaby’s Cockatoo, this project has also highlighted a number of crucial data gaps
and suggested priorities for future research, as outlined in Section 4.3.
It is important to acknowledge that there are still a number of uncertainties in the understanding of Carnaby’s
Cockatoo ecology. Most notably in this context the outputs of the PVA and modelled scenarios should be
viewed as indicators of likely trends rather than exact outcomes. Further research is recommended to
improve the PVA model reliability and to enhance understanding of Carnaby’s Cockatoo in general.
Parsons Brinckerhoff | 2189220A PR_0164 23
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
It is also the case that environmental and demographic stochasticity have not been explicitly modelled in this
PVA as suitable data were not available. Suitable data is likely to become available in the future through
additional research.
The range of Carnaby’s Cockatoo is thought to have contracted by > 30% since the late 1940s (Mawson and
Johnstone), and the species is regarded as having disappeared from >33% of its former breeding range
between 1968 and 1990 (Saunders and Ingram 1998), coincident with the estimated reduction in population
size.
4.2.1
Critical life history parameters
Critical life history parameters are considered to be those parameters that are likely to more strongly impact
population viability. It is these life history parameters that need to be focussed on to work towards a viable
species population scenario. The following parameters are considered to be critical for management of the
species:

breeding success (fecundity)

breeding habitat availability and location

foraging habitat availability and location

hollow abundance and annual rates of loss or degradation

mortality

age structure.
Additional information is needed on all of these parameters through further research requirements, as
outlined further in Section 4.3.
4.2.2
Parameters sensitive to data variations
Assumptions about the proportion of Carnaby’s Cockatoo pairs that can breed in a given year (10%, 16%
and 30%) lead to variability and uncertainty in the PVA model outputs. Whilst the impact of 16% and 30%
estimates on the model run for Scenario 1 are similar (Figure 2.4), an estimate of 10% leads to a greater
impact of Scenario 1 on the population of Carnaby’s Cockatoo in the Perth and Peel regions.
The PVA is sensitive to the proportion of Carnaby’s Cockatoo pairs that can breed in a given year parameter,
and therefore refinement of this parameter should be a high order priority for future research and PVA model
development.
4.2.3
Significance of habitat loss
The slow life history of Carnaby’s Cockatoo, where animals have a low fecundity but long lifespan, results in
populations that are significantly affected by processes that impact the carrying capacity. This PVA process
has suggested that this is the case with low population variability and a population that is maintained at the
carrying capacity when there are stable conditions prevailing. However, it should be noted that this is based
on short-term data and therefore would exclude processes that increase variability such as catastrophic
mass mortality events.
There are two major factors which impact the carrying capacity for the Carnaby’s Cockatoo population.
These are:

limited food resources, such as plantation pine and native vegetation

availability of nesting hollows and surrounding foraging habitat.
Parsons Brinckerhoff | 2189220A PR_0164 24
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
The degree to which these two factors impact the population is unknown however these factors are critical
for the Carnaby’s Cockatoo as they are essentially the ‘building blocks’ of any species. While it could appear
obvious that removal of foraging or breeding habitat would reduce the carrying capacity of any species, the
assessed scenarios are useful to indicate what general trends could be expected under different iterations of
foraging and breeding habitat loss or gain.
The scenarios for habitat clearing and habitat restoration (gain) are based on an assumption that the carrying
capacity for both food resources and breeding habitat is currently equal. It is unlikely this is the case, but this
represents the worst-case scenario. If one of these carrying capacities is higher than the other, then it
creates a buffer for the higher carrying capacity. For example, if the population is limited by nesting hollows
and has enough food for 40,000 individuals, then the removal of foraging habitat is unlikely to have an
impact on the population.
In all scenarios, an increase of habitat can only occur via habitat restoration resulting in additional habitat
being created over and above that which exists already. While offsetting existing habitats increases
protection of habitat for existing birds, it does not increase the carrying capacity overall.
These scenarios have focused on non-breeding food resources and not included feeding vegetation during
the breeding period, though this may also represent a limiting factor on the population. Breeding hollows
require a close association with feeding grounds. The limiting factor for the population may in fact be feeding
grounds near breeding hollows, and not just the number of breeding hollows. The interrelationship of these
factors is very complex and the current data and PVA does not incorporate this factor of complexity.
Scenarios of clearing are based on an assumption that all birds in the northern population are reliant on pine
plantations for survival. It should be noted that this is the worst-case scenario as the size of the population
that is reliant on the pine resource is unknown. Clearing of habitat was modelled to occur over twenty years
as this was thought to be a reasonable period over which the estimated habitat loss would occur.
The modelling predictions for each scenario are:






Scenario 1 – results in the population continuing at its current levels (which may include an ongoing
decline).
Scenario 2 – predicts a sharp decline in the population, possibly leading to inbreeding and/or extinction.
Scenario 3 – predicts a gradual recovery in the population over 25 years, assuming that the low
population base has survived.
Scenario 4 – predicts no improvement in the population. Essentially this means that you can improve
breeding conditions (i.e. hollows) but if habitat is not replaced or protected the population will not
recover.
Scenario 5 – predicts the most rapid recovery of the population, meaning that substantial habitat
restoration combined with breeding hollow creation will produce recovery (but this is over 20 years).
Scenario 6 – predicts recovery with combined foraging and breeding habitat creation, requiring less
effort to recover the population from a better base population.
The trend shown in the modelled Scenarios 2 and 4 confirm that loss of foraging habitat in the Perth and
Peel regions will have a negative impact on the population size of Carnaby’s Cockatoo, and that restoration
attempts which include measures to improve breeding success without concomitant foraging habitat
availability will fail to produce satisfactory rates of recovery.
Parsons Brinckerhoff | 2189220A PR_0164 25
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
4.3
Data gaps and future research priorities
The PVA has enabled the identification of many data gaps, which could form the basis of future research
focus for Carnaby’s Cockatoo. This is a reflection of the primary value of the current Carnaby’s Cockatoo
PVA in pointing to parameter sensitivities and data gaps.
Assumptions about the proportion of Carnaby’s Cockatoo pairs that can breed in a given year (10%, 16%
and 30%) lead to variability and uncertainty in model outputs. Whilst the impact of 16% and 30% estimates
on the model run for Scenario 1 are similar (Figure 2.4), an estimate of 10% leads to a greater impact of
Scenario 1 on the population of Carnaby’s Cockatoo in the Perth and Peel regions. The PVA is sensitive to
the proportion of Carnaby’s Cockatoo pairs that can breed in a given year, and therefore refinement of this
parameter should be a high order priority for future research and PVA model development.
The availability of nest hollows suitable for use by Carnaby’s Cockatoo is indicated as a limiting resource for
the species, but no data exist to quantify this resource across the range of the species. A study to quantify
the number of breeding hollows that are available for Carnaby’s Cockatoo to use, the variability in breeding
hollow abundance or availability between years and any long-term trends in breeding hollow availability, is
recommended. If breeding habitat is the major restriction of the population, it may provide a highly costeffective component of any mitigation strategy as a nesting bird requires 0.5 breeding hollows compared to
approximately three hectares of feed trees. However, if this factor is not limiting the population it would
provide no benefit. This is considered to be a critical factor for future research.
Carnaby’s Cockatoo numbers directly associated with plantation pines have been estimated from non-survey
data, but is indicated as a limiting resource for the species in the current Perth and Peel regions. A study to
quantify the identity (in terms of breeding location association) and number of Carnaby’s Cockatoo directly
reliant on the pine plantations is recommended. If pine removal occurs it should be concurrent with a study
on the impact on population and movement.
Long-term demographic studies of both subpopulations of Carnaby’s Cockatoo would be needed to permit
the evaluation of impact of stochastic processes on the population (including catastrophic mass mortality
events). This should include scientific research to obtain more accurate data on population numbers, as
knowing a reliable estimate of the population will mean that predictions of species viability will also be more
reliable. This is important for the conservation management of the species.
Further research should also be conducted on habitat quality of different vegetation types and food plant
species. This could be incorporated into any future modelling for the species.
Parsons Brinckerhoff | 2189220A PR_0164 26
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report
5. Conclusion
The PVA has enabled the identification of many data gaps, which could form the basis of future research
focus for Carnaby’s Cockatoo. This is a reflection of the value of the current Carnaby’s Cockatoo PVA in
pointing to parameter sensitivities and data gaps.
The PVA is sensitive to the proportion of Carnaby’s Cockatoo pairs that can breed in a given year parameter,
as well as the estimate of post-fledging survival. Therefore refinement of these parameters should be a high
order priority for future research and PVA model development.
As the population of Carnaby’s Cockatoo is assumed to be functioning at close to the foraging and
reproductive carrying capacity, it is unsurprisingly the case that development scenarios which result in a loss
of either foraging or breeding habitat have a negative impact on the population size trend.
It is possible that the current population is continuing to experience decline due to past habitat degradation
which in turn reduces carrying capacity. If this is the case, the population trajectories from further clearing
scenarios will have a larger effect than is predicted by this PVA model.
The scenarios outlined and modelled in Section 3 only provide a general indication of trends for each of the
hypothetical scenarios. The greatest value of undertaking a PVA is for this reason, however due to the
complex interaction of PVA parameters of varying reliability, focus should not be on raw numbers.
Conservatively, the model limitations mean that the trends shown for each scenario are likely to
underestimate the impacts of foraging and breeding habitat removal. This is despite the use of parameters
thought to be the most reasonable and accurate at the time of modelling.
The trend shown in the modelled scenarios 2 and 4 confirm that loss of foraging habitat in the Perth and Peel
regions will have a negative impact on the population size of Carnaby’s Cockatoo, possibly leading to
species extinction. This means that if clearing continues to occur at its current rate without effective habitat
restoration, the northern sub-population is likely to decline to extinction in less than 20 years.
Restoration attempts which include measures to improve breeding success without concomitant foraging
habitat availability will most likely fail to produce satisfactory rates of recovery.
In general, the scenarios demonstrate that reducing habitat clearance combined with minimising the gap
between the impact of any clearing and the value of restored habitat will aid the viability of this species in the
future. It is also evident that avoiding clearing of habitat early would reduce the amount of subsequent
restoration needed.
The urban consolidation scenario results in the best modelled outcome for Carnaby’s Cockatoo population
apart from the scenario showing immediate ceasing of any habitat clearing.
Another important outcome from the scenario analysis is that both foraging and breeding habitat should be
restored in tandem to gain the best improvement in population numbers.
The following research is recommended for prioritisation to assist in refinement of critical life history
parameters and change scenarios in this or a future PVA model:

identification of reliable estimates for the total extant population and sub-populations

identification of a reliable figure for the proportion of Carnaby’s Cockatoo pairs that can breed

quantification of nest hollow abundance and annual rates of loss or degradation in breeding habitats
Parsons Brinckerhoff | 2189220A PR_0164 27
Department of Sustainability, Environment, Water, Population and Communities Carnaby's Cockatoo
Population Viability Analysis Model Report

documenting the increase in breeding success where additional nest hollows are provided

refining mortality knowledge through further directed research and opportunistic data collection

refining knowledge of age structure of the population through further directed research and opportunistic
data collection


quantification of numbers and origin of Carnaby’s Cockatoo directly reliant on the plantation pine habitat
research should also be conducted on habitat quality of different vegetation types and food plant
species.
It is also recommended that research to address limitations of the current PVA (which does not consider
spatial and temporal variability and environmental stochasticity) be prioritised:

generation of long-term demographic models to enable incorporation of stochastic impacts on the
population

pursuit of spatial analysis of discreet local populations including dispersal between these populations.
Parsons Brinckerhoff | 2189220A PR_0164 28
6. References

Brook, B.W., O'Grady, J.J., Chapman, A.P., Burgman, M.A., Akçakaya, H.R. & Frankham, R. (2000)
Predictive accuracy of population viability analysis in conservation biology. Nature, 404, 385–387.

de Magalhães, J.P., Costa, J., & Church, G.M. (2007). An Analysis of the Relationship Between
Metabolism, Developmental Schedules, and Longevity Using Phylogenetic Independent Contrasts The
Journals of Gerontology Series A: Biological Sciences and Medical Sciences 62: 149–160.

Department of Environment and Conservation (DEC) (2012) Carnaby’s Cockatoo (Calyptorhynchus
latirostris) Recovery Plan. Western Australian Wildlife Management Program No. 52. Department of
Environment and Conservation (DEC), Perth.

Higgins, P. J. (1999). Handbook of Australian, New Zealand and Antarctic Birds Volume 4: Parrots to
Dollarbird. Oxford University Press., Melbourne.

Holmes, D.J. & Austad, S.N. (1995). The evolution of avian senescence patterns: implications for
understanding primary aging processes. American Zoologist 35:307–317.

Johnstone, R.E. & Kirkby, T. (2005) Cockatoos in crisis. Landscope, 21, 59–61.

Jupp, T. (1996) Carnaby's Cockatoo - preventing a crisis! Psittascene, 8, 8–9.

Kabat, T.J., Barrett, G. & Kabat, A.P. (2012). 2012 Great Cocky Count: Identification of roost sites for
Carnaby’s Black-Cockatoo (Calyptorhynchus latirostris) and population count for the DEC Swan Region.
Final report 2012. BirdLife Australia, Perth.

Lacy, R.C., Borbat, M. & Pollak, J.P. (2013) VORTEX: A Stochastic Simulation of the Extinction
Process.Version 9.99. Chicago Zoological Society.

Madsen T., Stille B. & Shine R. (1996) Inbreeding depression in an isolated population of Adders Vipera
berus. Biological Conservation 75, 113–8.

Mawson, P. & Johnstone, R. (1997) Conservation status of parrots and cockatoos in Western Australia.
Eclectus, 2, 4-9.

Miller, P.S. & Lacy, R.C. (2005) VORTEX: A Stochastic Simulation of the Extinction Process. Version
9.50 User’s Manual. Conservation Breeding Specialist Group (SSC/IUCN), Apple Valley, MN.

Mooney, P.A. & Pedler, L.P. (2005) Recovery plan for the South Australian subspecies of the Glossy
Black-Cockatoo (Calyptorhynchus lathami halmaturinus): 2005-2010 South Australian Department for
Environment and Heritage, Adelaide.



Parsons Brinckerhoff (2013) Carnaby’s Cockatoo - Population Viability Analysis (PVA) literature review.
Parsons Brinckerhoff, Perth.
Reed D. H., O'Grady J. J., Brook B. W., Ballou J. D. & Frankham R. (2003) Estimates of minimum viable
population sizes for vertebrates and factors influencing those estimates. Biological Conservation 113,
23–34.
Saunders, D. & Dawson, R. (2009) Update on longevity and movement of Carnaby’s Cockatoo. Pacific
Conservation Biology, 15, 72–74.

Saunders, D.A. (1982) The breeding behaviour and biology of the short-billed form of the White-tailed
Black Cockatoo Calyptorhynchus funereus. Ibis, 124, 422–455.

Saunders, D.A. (1986) Breeding season, nesting success and nestling growth in Carnaby's Cockatoo,
Calyptorhynchus funereus latirostris, over 16 years at Coomallo Creek, and a methods for assessing
the viability of populations in other areas. Australian Wildlife Research, 13, 261–273.

Saunders, D. A. and J. A. Ingram. (1998). Twenty-eight years of monitoring a breeding population of
Carnaby's Cockatoo. Pacific Conservation Biology 4:261–270.

Skalski, J.R., Ryding, K.E. & Millspaugh, J.J. (2005) Wildlife Demography: Analysis of Sex, Age and
Count Data. Elsevier, Sydney.

Smith, G.T. & Saunders, D.A. (1986) Clutch size and productivity in three sympactric species of
Cockatoo (Psittaciformes) in the south-west of Western Australia. Australian Wildlife Research, 13,
275–285.

Stock, W.D., Finn, H., Parker, J. & Dods, K. (2013) Pine as Fast Food: Foraging Ecology of an
Endangered Cockatoo in a Forestry Landscape. PLoS One, 8, e61145.

Thackway, R. and Cresswell, I.D. (1995). An interim biogeographic regionalisation for Australia: a
framework for setting priorities in the National Reserves System Cooperative Program, Version 4.0.
Australian Nature Conservation Agency, Canberra.

Traill L. W., Bradshaw C. J. A. & Brook B. W. (2007) Minimum viable population size: A meta-analysis of
30 years of published estimates. Biological Conservation 139, 159–66.

Warren, K., Le Souëf, A., Holyoake, C., Yeap, L., Calver, M., Finn, H., Cooey, C., Johnston, R.,
Saunders, D., Dawson, R., Mawson, P., Vitali, S. & Klandorf, H. (2013 in prep.) Determination of age
and sex structure demographics of Carnaby’s cockatoos (Calyptorhynchus latirostris) from two wild
populations in the south-west of Western Australia. Biological Conservation.
Appendix A
Modelling scenarios
Appendix B
Literature review