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

Abstract

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. Show more