Science for Saving Species Research findings factsheet Project 4.2.3

Resurrecting the Macquarie Island red-crowned parakeet

In brief

Macquarie Island, an Australian We aimed to determine which sister red-crowned parakeet (Reischek’s sub-Antarctic island, has undergone species may be most suitable for parakeet) as the most suitable successful eradication of multiple an introduction, restoring roles in species for the introduction to invasive mammals, including the ecosystems that disappeared Macquarie Island. This allows any predators that drove the extinction when the species went extinct. future assessment to focus on of the endemic Macquarie Island this species. We developed a new decision red-crowned parakeet in the 1880s. framework, which can overcome An additional benefit is that the This study examined replacing the the issue of not knowing which introduction offers the opportunity extinct parakeet species with a factors, such as climate and to create an insurance population closely related surviving species. vegetation type, will be of greatest for Reischek’s parakeet, which Four other species of red-crowned importance in determining suitability, occurs on only one small island. parakeets occur on New Zealand by considering a range of scenarios. Our decision framework will be islands that are geographically of use to others pursuing Applying this framework consistently close and environmentally similar restorative island restoration. identified the Antipodes Island to Macquarie Island.

Red-crowned parakeet Cyanoramphus. n. novaezelandiae, Enderby Island. Image: Aleks Terauds

Further Information Justine Shaw - [email protected] Hannah Wauchope - [email protected] Megaherbs (Pleurophyllum hookeri) on Macquarie Island. image: Justine Shaw Coastal habitat on Macquarie Island. Image: Justine Shaw

Background

Reintroducing species to islands, These invasive predators multiple closely related extant or introducing species to islands as contributed to the extinctions not species. Cyanoramphus parakeets havens, are topics attracting much only of the Macquarie Island red- are naturally distributed throughout conservation interest and effort. crowned parakeet (Cyanoramphus New Zealand and on many offshore These introductions, which involve novaezelandiae erythortis) in the and sub-Antarctic islands. They are people intentionally moving a species 1800s but also the Macquarie separated by crown colour, with outside its natural range to achieve Island buff-banded rail (Gallirallus the extinct Macquarie Island conservation goals, are becoming philippensis macquariensis). Cat parakeet belonging to the red- an increasingly relevant strategy to eradication was declared a success crowned clade, or group, of species. help restore, maintain and protect in 2002, and a program to eradicate The remaining four populations biodiversity in a rapidly changing rabbits, rats and mice was declared from this clade occur on islands world. Island species are among successful in 2014. The island is now that are geographically close or the most threatened globally, officially free of invasive mammals. environmentally similar to Macquarie and present particular opportunities Island: C. n. novaezelandiae on the Given this success, there is now and challenges for such strategies. Auckland Islands and Stewart Island; an opportunity to focus on further Reischek’s parakeet (C. hotchstetteri) Macquarie Island, a sub-Antarctic restoration, including bringing one of World Heritage Site and Tasmanian on Antipodes Island; and C. n. the closely related extant red-crowned Nature Reserve, has recently undergone chathamensis on the Chatham parakeet species to Macquarie Island. a major conservation restoration. Islands (see Figure 1). Given this Natural colonisation is unlikely in Invasion by several vertebrates, array of related species, how do the foreseeable future due to the including rats, Weka (Gallirallus australis), we determine which would provide extreme isolation of the island. mice, rabbits and cats had caused the best potential source population devastating impacts on vegetation In the case of the Macquarie Island for a conservation reintroduction and predation on native species. red-crowned parakeet, there are to Macquarie Island?

Research aims

We aimed to determine how to choose the best sister species as a source population for translocation to Macquarie Island New Zealand Mainland to replace the Macquarie Island C. novaezelanidae parakeet. Proactively introducing a closely related species may have multiple benefits. First, it may enhance the island’s ecosystems and values, Chatham Islands C. n. chathamensis through the parakeets’ role in seed Stewart Island dispersal, which would help with C. n. novaezelanidae island. Second, it may provide an additional insurance population for the chosen species. Auckland Islands Antipodes Island C. n. novaezelanidae C. hotchstetteri

Macquarie Island C. (n.) erythrotis (extinct)

Figure 1. New Zealand and surrounding islands, showing populations of the red-crowned clade of parakeets, Cyanoramphus novaezelandiae. The mainland population is presumed extinct. What we did

To determine the relative suitability Because we don’t know whether of all closely related red-crowned certain habitat variables are more parakeets for introduction to important to the parakeets than Macquarie Island, we undertook others, we iteratively weighted structured decision-making, using different variables to see if different a systematic four-step process: source populations performed better when different variables 1. Identify the suite of potential were weighted highly. source populations The six variables we chose were 2. Identify attributes that can be (1) beta diversity, that is, the similarity used to choose among the of vegetation between the two possible source populations islands; (2) maximum temperature; 3. Weight these attributes according (3) minimum temperature; (4) rainfall; to which are likely to be the most (5) tree presence; and (6) distance important to source population to Macquarie Island. To weight the survival on Macquarie Island. relative importance of attributes, we Figure 2. Relative suitability scores of 4. Rank the suitability of the sources ran six analysis iterations. In each, four potential source populations of by summing the attribute values we chose one attribute, weighted Cyanoramphus species parakeets being considered for a conservation introduction by the attribute weights for each. it as x times more important than the others, combined attribute values to Macquarie Island. The higher the score, First, we gathered information about the greater the suitability for translocation with these weights, and determined between that source and Macquarie Island, the populations of red-crowned which source population was the relative to other sources. As it is unknown parakeets on neighbouring islands most suitable. We then repeated which of the variables considered will be of and quantified various habitat variables the process for values of x of 2, 4, most importance in determining suitability, (listed below) to see which habitats we ran scenarios with attributes weighted 6 and 8 (see Figure 2). differently – symbols indicate which attribute were most similar to Macquarie Island. was weighted as x times (2, 4, 6 or 8) more important in that iteration.

Key findings

In this project, we developed a new An incidental advantage of this choice parakeet on Antipodes Island are also decision framework for choosing the is that Reischek’s parakeet comprise present on Macquarie Island, and most appropriate source population only a very small wild population, given that red-crowned parakeets to replace an extinct species on which only occurs on a tiny island are adaptable with a varied diet, their an island. This novel framework (22km2 cf. Macquarie Island, dietary needs are likely to be met. determined that the species that 127.8km2), and could benefit in Reintroduction of Reischek’s parakeet lives on Antipodes Island, Reischek’s the future from the establishment may therefore fulfil an ecosystem parakeet, consistently performed of an insurance population. niche that can contribute to ongoing as the most suitable choice for an restoration of vegetation on post- While the exact functional role of the introduction to Macquarie Island eradication Macquarie Island. extinct Macquarie Island parakeet to replace the extinct Macquarie cannot now be properly understood, Island parakeet. Megaherbs (Pleurophyllum hookeri, Stilbocarpa elsewhere the closely related sister polaris). Image: Justine Shaw Regardless of which attribute was species of red-crowned parakeets heavily weighted, Reischek’s parakeet forage on seeds and berries, and from Antipodes Island outperformed may contribute to plant propagule the others in almost all cases; only dispersal, especially in the light of when distance to Macquarie Island prior research that indicates that the was weighted ≥6 times more role of parrots as seed dispersers has important than other attributes did the been widely overlooked. Most plant Auckland Island parakeet outperform it. species consumed by Reischek’s Red-crowned parakeet. Image: Aleks Terauds

Applications Recommendations

This research presents a structured Our research gives some general way to identify suitable source recommendations for scientists and populations to replace extinct managers when they are considering species from island ecosystems. restoring island biodiversity after As eradication of invasive species an eradication. It is essential to first on islands increases worldwide, determine whether any surrogate opportunities for proactive, or sister species may be suitable for restorative conservation are introduction and therefore able to going to become increasingly restore roles in the ecosystems that commonplace, and our method disappeared with the extinct species. provides structure and guidance Look to neighbouring populations or to the first step in the process. sister species from similar ecosystems Macquarie Island ecosystem. As such, it will be of most and determine their suitability to Detailed research will be required importance to island ecologists, the newly restored island habitat. to determine the health and robustness island managers, restoration of the source population. Already we With regard to the restoration of ecologists, translocation scientists know that Reischek’s parakeet survived parakeets to Macquarie Island, what and eradication scientists. It will be well in captivity during the recent we have achieved via our novel of further practical use to island mouse eradication on Antipodes decision framework is a narrowing restoration teams, sub-Antarctic Island, and the immediate impact of the field of potential sister species island managers, the New Zealand on the source population of keeping so that further analysis assessing Department of Conservation, these individuals captive did not suitability can be conducted for and staff of the Lord Howe and appear to be severe. While research Reischek’s parakeet, the population Norfolk Island National Parks. shows many species of bird and best suited to Macquarie Island. animals naturally move between these Identifying the most suitable source islands, the consideration of legal species allows a management focus Short grassland on Macquarie Island. requirements and any biosecurity on that sole species for further Image: Justine Shaw risks are obviously essential prior assessment of diet, physiological to a reintroduction. While there constraints, habitat, behavioural has never been a conservation requirements, and impacts to source introduction to Macquarie Island, population and recipient ecosystem. it is not unprecedented to introduce This research aims to help identify new species to Macquarie Island suitable source populations. Once for management purposes: the appropriate source populations European rabbit flea (Spilopsyllus have been identified there are cuniculi), myxoma virus and rabbit obviously multiple considerations haemorrhagic disease virus have all prior to a reintroduction taking been introduced to the island. Now place. Consideration is needed to that eradication of vertebrate mammals Cited material determine whether there are likely is completed for the island, managers to be any perverse outcomes from are left to determine what restoration Wauchope, H. S., Fuller, R. A., reintroducing a parakeet to the “looks like” for Macquarie Island. Shanahan, D. F., & Shaw, J. D. 2018. Restoring islands and identifying source populations for Further Information introductions. Conservation Biology Justine Shaw - [email protected] 33(3), 729–732. Hannah Wauchope - [email protected]

This project is supported through funding from the Australian Government’s National Environmental Science Program.