GPS telemetry facilitates the identification of forage plant species for endangered Carnaby’s cockatoos (Zanda latirostris) at inland breeding sites and post-breeding dispersal locations in Western Australia

Introduction

Habitat loss and fragmentation are major threats to wildlife globally (Sullivan et al. 2021; de Souza Leite et al. 2022). This is particularly so for Carnaby’s cockatoos (Zanda latirostris), an iconic Western Australian species that has experienced a decline in population and a 30% range contraction over the past century (Saunders 1990), with a recently estimated reduction of 2% annually between 2010 and 2022 (Pryor et al. 2023). Carnaby’s cockatoos are listed as Endangered under both state and Australian federal law, and internationally by the IUCN (Department of Environment and Conservation 2012). The Carnaby’s cockatoo distribution is within the Southwest Australian Floristic Region (SWAFR) (Fig. 1), known for its species richness and endemism.

Fig. 1.

Carnaby’s cockatoo distribution range and the Southwest Australian Floristic Region including Interim Biogeographical Regionalisation for Australia (IBRA) regions. Breeding grounds related to this study are named on the map with a black dot. Major cities are marked with a black square and written in capital letters. Non-breeding dispersal locations where some of the forage species from this study were identified are in Table 1.

Proponents seeking approval to clear land impacting Carnaby’s cockatoo foraging or breeding habitat must provide a detailed habitat assessment, showing they have surveyed its suitability for use by black cockatoos. According to the Australian ‘Federal Referral Guidelines for Black Cockatoos’ (DAWE 2022) (hereafter the Referral Guidelines), actions resulting in loss of foraging habitat may require referral to the Minister for the Environment and Water for approval. To determine whether a particular patch of habitat is suitable for use by black cockatoos it is assessed according to the ‘Scoring Tool Template’ found within the Referral Guidelines, which considers the condition, context and stocking rate of habitat patches. This template also states that a site will start with the maximum ‘score’ if it contains known foraging species. The Referral Guidelines state that habitat assessments must be sufficient to complete the ‘Scoring Tool’ and must consider key attributes including foraging potential and habitat patch connectivity, with a view to meeting the standard of ‘no net loss’ of habitat over time (Maron et al. 2010, 2021; DAWE 2022).

When conducting habitat assessments for black cockatoos, environmental consultants often refer to the list in ‘Plants Used by Carnaby’s Black Cockatoo’ (Groom 2011) and the ‘Scoring system for the assessment of foraging value of vegetation for Black-Cockatoos’ (Bamford 2020). The scoring tool described by Bamford (2020) states that if known food plants exist in a habitat patch is to be cleared, then the patch will score higher accounting for its foraging value. It is the list from Groom (2011) that most consultants refer to during this assessment process for guidance regarding known forage species. The list is comprehensive (Groom 2011), but mainly contains species found on the Swan Coastal Plain; Interim Biogeographical Regionalisation for Australia (IBRA) region Swan Coastal Plain (SWA) (DCCEEW 2023); an area utilised by Carnaby’s cockatoos during the non-breeding season. It does not document many Carnaby’s cockatoos forage species found in other parts of their distribution, particularly from the northern, southern and inland areas where most breeding occurs (Saunders 1974).

To aid in the conservation and retention of Carnaby’s cockatoo’s habitat, it is important to assess foraging habitat suitability across their whole distribution, not only within the SWA. To fill this knowledge gap, we used direct observation and GPS telemetry to identify plant species foraged on by Carnaby’s cockatoos outside the SWA region. Globally, the use of GPS telemetry (and movement ecology data) has facilitated greater understanding of the foraging ecology of many species, with tracking devices providing accurate location data that can be used to determine where and on what animals are foraging (Nathan et al. 2008; Joo et al. 2022). This information is particularly important for endangered species as knowledge about their foraging ecology and dietary preferences can facilitate the conservation and protection of patches containing key food resources. Here, we present an updated forage list for Carnaby’s cockatoos compiled during a broader telemetry study into the movement ecology of this species.

Materials and methods

Results

A total of 44 native plant species, additional to the ones in Groom’s (2011) list, were identified as Carnaby’s cockatoo forage species. Most of the species identified were from the Proteaceae family, and were either in the Banksia (n = 22) or Hakea (n = 10) genus. Genera that were not in Groom’s (2011) list but identified in this study include Adenanthos, Allocasuarina, Daviesia, Mesomelaena, and Xylomelum (Table 1). A total of 410 days were spent in the field collecting data and observations. All observed foraging was of flocks ranging in size from 30 to 800 birds. Forage patches generally comprised multiple plant species and it was common to see different birds in the same flock feeding on different species. Typically, average daily foraging distance travelled for incubating or provisioning Carnaby’s cockatoos was 5.92 ± 4.40 km).

Discussion and conclusion

Of the SWAFR’s nine IBRA7 regions, Carnaby’s cockatoo’s distribution extends across eight IBRA7: (1) Avon Wheatbelt; (2) Coolgardie; (3) Esperance Sandplains; (4) Geraldton Sandplains; (5) Jarrah Forest; (6) Mallee; (7) Swan Coastal Plain; and (8) Warren (Lambers 2014; Brundrett 2021). The list from Groom (2011) contains plants found in several of these regions but was compiled from research concentrated in coastal urban or peri-urban areas. Our updated list adds species found in all nine of the SWAFR IBRA7 regions and, in addition to the SWA, was compiled from research at inland breeding grounds and along post-breeding dispersal routes. This incorporates a broader extent of the Carnaby’s cockatoo’s distribution and will facilitate improved habitat suitability assessment across the species breeding and non-breeding spatial range.

To adequately assess habitat patches for their value, information regarding the foraging ecology of the animal species using these patches is critical. With the aid of GPS telemetry, we have identified and added 44 new forage species and five new genera to the existing forage species list and increased the spatial coverage of known forage species across more of the Carnaby’s cockatoos distribution range. This information will inform regulators on the potential use of habitat patches by Carnaby’s cockatoos, aiding decisions around habitat clearing, protection and conservation.