Is It Benign or Is It a Pariah? Empirical Evidence for the Impact of the Common Myna (Acridotheres tristis) on Australian Birds

There is widespread concern over the impact of introduced species on biodiversity, but the magnitude of these impacts can be variable. Understanding the impact of an introduced species is essential for effective management. However, empirical evidence of the impact of an introduced species can be difficult to obtain, especially when the impact is through competition. Change in species abundance is often slow and gradual, coinciding with environmental change. As a result, negative impacts on native species through competition are poorly documented. An example of the difficulties associated with obtaining empirical evidence of impact due to competition comes from work on the Common Myna (Acridotheres tristis). The species is listed in the World's top 100 worst invaders, despite a lack of empirical evidence of its negative impacts on native species. We assessed the impact of the Common Myna on native bird abundance, using long-term data both pre and post its invasion. At the outset of our investigation, we postulated that Common Myna establishment would negatively affect the abundance of other cavity-nesting species and bird species that are smaller than it. We found a negative relationship between the establishment of the Common Myna and the long-term abundance of three cavity-nesting species (Sulphur-crested Cockatoo, Crimson Rosella, Laughing Kookaburra) and eight small bird species (Striated Paradoxes, Rufous Whistler, Willie Wagtail, Grey Fantail, Magpie-lark, House Sparrow, Silvereye, Common Blackbird). To the best of our knowledge, this finding has never previously been demonstrated at the population level. We discuss the key elements of our success in finding empirical evidence of a species impact and the implications for prioritisation of introduced species for management. Specifically, prioritization of the Common Myna for management over other species still remains a contentious issue.This work is supported in part by the Invasive Animals Cooperative Research Centre and the Australian National University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Testing multiple pathways for impacts of the non-native Black-headed Weaver Ploceus melanocephalus on native birds in Iberia in the early phase of invasion

Not all non-native species have strong negative impacts on native species. It is desirable to assess whether a non-native species will have a negative impact at an early stage in the invasion process, when management options such as eradication are still available. Although it may be difficult to detect early impacts of non-native species, it is necessary to ensure that management decisions can be based on case-specific scientific evidence. We assess the impacts of a non-native bird, the Black-headed Weaver Ploceus melanocephalus, at an early stage in its invasion of the Iberian Peninsula. To do this we identify potential pathways by which competition for shared resources by Black-headed Weavers could lead to population declines in two ecologically similar native species, and generate hypotheses to test for evidence of competition along these pathways. Black-headed Weavers could potentially impact native species by displacing them from nesting habitat, or by reducing habitat quality. We found no evidence for either potential competition pathway, suggesting that Black-headed Weavers do not currently compete with the two native species. However, it is possible that mechanisms that currently allow coexistence may not operate once Black-headed Weavers reach higher population densities or different habitats

The introduction, spread, impact and control of the common myna (Acridotheres tristis)

The common myna (Acridotheres tristis) has been introduced throughout the world primarily to control insect pests in agriculture. However, the common myna has now been listed in the world's top 100 worst invaders. There is global concern that the common myna may negatively impact other species through territorial exclusion and cavity-nesting competition. As such, there is growing demand for management strategies to control the species. Despite this concern, there is limited scientific evidence regarding the impact of the common myna. Some research even suggests the impact of this species is over stated or nonexistent. Therefore, it is imperative that the population dynamics and potential impact of this species are understood. This thesis comprises five research articles that investigate the introduction, spread, impact and control of the common myna. To examine the introduction and spread of the common myna, a composite 41-year data set was used to reconstruct the species invasion sequence. The impact of the common myna on native bird abundance was then assessed, using long-term data both pre and post invasion. A negative relationship between the establishment of the common myna, and the long-term abundance of three cavity-nesting species and eight small bird species, was observed. This finding has never previously been demonstrated at the population level. Using 1071 transect bird surveys, the impact of the common myna in conjunction with habitat modification was then investigated. This study indicated that common myna abundance is strongly influenced by habitat. However, negative associations between common myna abundance and some bird species were also observed. To investigate cavity-nesting competition, 225 nest boxes were established and monitored over three breeding seasons. This study provides the strongest evidence to date for a negative impact of the common myna on native birds through cavity-nesting competition. Finally, the impact of a community common myna culling program was assessed using transect surveys and a population model. Reductions in common myna abundance were related to high intensity culling across small-scale areas. However, the results indicate that too few individuals are being removed to have a broad scale influence. The elements for a successful control program and methods to increase the effectiveness of culling programs are discussed. This thesis provides a comprehensive investigation into the ecology of the common myna and adds significant new knowledge on the invasion sequence, species impact (type and severity) and population dynamics of the common myna. An overarching finding of this thesis is the significant impact of habitat on species abundance. Therefore, to disentangle the impacts on native species, analysis must include both habitat variables and introduced species impact. Habitat modification can also influence the severity of introduced species impact and therefore potential management responses. Habitat restoration is recommended as an alternative method for common myna control that would also aid native species recovery

A citizen-trapper effort to control Common Myna: trap success, specificity and preferred bait type

We describe a community-run effort to cull Common Myna (Acridotheres tristis) in Melbourne undertaken with modest funding (overall: $30.14 per trap day,$5.17 per euthanized Common Myna). Trap success (overall, 0.04 birds per trap per day) peaked early in the effort and slowly declined. Trap specificity was high (83.8%) and similar between bait types. Dry cat food captured more Common Myna, and a similar assemblage of animals, to dry dog food. Bread baits captured a broader assemblage of animals. The community-led trapping programme reduced the mean density of Common Myna and achieved high target specificity with relatively few unintended trap deaths. While long-term impacts on the population of Common Myna or native birds are yet to be analysed, the results suggest that ongoing effort is required for population suppression.Grant D. Linley, David C. Paton, Michael A. Westo

Teachers' Perceptions of their Abilities to be Educational Leaders in Victorian Childcare Settings

IN THE CONTEXT OF NEW national regulatory requirements for designated educational leaders in early childhood settings, 11 Victorian teachers participated in semi-structured interviews exploring their perceptions of their ability to act as educational leaders in their childcare centres. Analysis of these interviews showed that, while teachers successfully made changes within their rooms, only those with a formal title or authority expressed confidence in their ability to lead change across their centres. Barriers to leadership included lack of time and a perception that their teacher qualifications ‘did not buy authority’. A hierarchical model of leadership appeared dominant within the centres. The findings suggest both time allowance and formal role designation as strategies to support the new leadership roles, but also raise questions about the most effective models for supporting teacher leadership in childcare contexts. </jats:p