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

Life Expectancy, Causes of Death and Movements of the Grey-Headed Flying-Fox (Pteropus poliocephalus) Inferred from Banding

This study was designed to generate information on demography and movements in large flying-foxes, information that is critical to management planning. Between 1989 and 2002, 2,244 wild grey-headed flying-foxes, Pteropus poliocephalus, were harp-trapped, banded and released at sites across south-eastern Australia; 918 hand-reared orphans were also banded and released at four sites. Retraps of wild animals were few (n = 10) and are not discussed here. Recoveries (n = 86) from the public reporting dead wild flyingfoxes (total 4.27%) and 38 hand-reared orphans (4.13%) are discussed. Recovery data were analysed via standard multiple regression; there was no difference between the sexes of wild P. poliocephalus in age at death or distance travelled, but hand-reared animals, on average, lived less than half as long as their wild counterparts (P < 0.001) and did not travel as far (P < 0.01). The average age of wild P. poliocephalus at death was 7.1 ± 3.9 years (0 ± SD, n = 86); the oldest flying-fox was 18 years of age. Generation length is estimated at 7.4 ± 3.76 years. Major causes of death of 86 wild P. poliocephalus were: hyperthermia (33.7%); electrocution (18.6%); entanglement in fruit-tree netting (5.8%); entanglement in barbed wire (4.7%); unknown (32.6%). 77% of recoveries of wild-banded P. poliocephalus were within 20 km of where they were banded; the longest movement recorded was 978 km. 1,632 wild black flying-foxes, P. alecto were trapped and banded; 27 were retrapped; seven were recovered dead (0.42%); from another 136 banded as hand-reared orphans, three were recovered (2.2%). Of 583 wild little red flying-foxes, P. scapulatus, trapped and banded, none were retrapped; one was recovered (0.2%). Data from P. alecto and P. scapulatus were too few for statistical analysis.This study was initiated with financial support from the Aus tralian National Parks and Wildlife Service, Earthwatch Australia, the Queensland Wildlife Protection Society and Wildlife Management Internationa

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

The bi-annual abundance (birds per km²) of small bird species (<25 cm head to tail) across four regions in the rural city of Canberra, South East Australia (Region 1: solid grey line, Region 2: dotted grey line, Region 3: solid black line, Region 4: dotted black line).

<p>The bi-annual abundance (birds per km²) of small bird species (<25 cm head to tail) across four regions in the rural city of Canberra, South East Australia (Region 1: solid grey line, Region 2: dotted grey line, Region 3: solid black line, Region 4: dotted black line).</p