Indian mynas: Scourge of native
birdlife, world-first research finds
THE common myna, or Indian myna bird, competes with native birdlife for food, nest sites and territory, adversely impacting native and other bird species, research has shown.
Data gathered by the Canberra Ornothologists Group over 29 years has assisted research by the Invasive Animals Co-operative Research Centre (IACRC) and the Australian National University (ANU), using Canberra as a case study, shows Indian mynas affect populations of the sulphur-crested cockatoo, crimson rosella, laughing kookaburra, superb fairy-wren, striated pardalote, Willie wagtail, grey fantail, magpie-lark, silvereye and common blackbird, says the IACRC.
PhD Candidate Kate Grarock, with the IACRC at ANU, says that to the best of our knowledge, these findings for the Indian myna have never previously been demonstrated at the population level anywhere in the world.
For instance, sulphur-crested cockatoo abundance in Canberra prior to establishment of an Indian myna population increased throughout the survey period by an estimated 10.3 birds per square kilometres (sq km) each year. However, after Indian myna establishment, growth in sulphur-crested cockatoo abundance reduced by an estimated two birds per sq km each year.
Crimson rosella abundance increased throughout the survey period by an estimated 5.9 birds per sq km each year.
However, after Indian myna establishment, growth in abundance declined by an estimated 3.5 birds per sq km each year.
Laughing kookaburra abundance was relatively stable throughout the survey period. However, after Indian myna establishment, abundance reduced by an estimated 0.4 birds per sq km each year.
“Indian mynas affect native and other birds in three ways,” says Ms Grarock.
“They compete for food. They compete for cavity-nesting sites, so reducing the breeding success of other species. They compete for territories.
“The Indian myna actively defends up to three hectares and feeds within an area of up to two kilometres from a communal roost and builds and defends multiple nests as a deterrent to other cavity-nesting species.”
Ms Grarock says previous attempts to investigate Indian myna impact have relied on short-term data (from one to three years) with limited success.
The Canberra Indian myna research used long-term data gathered by the Canberra Ornithologists Group over 29 years, and provided a unique opportunity to present the strongest evidence to date for the impact of the Common Myna on native and other bird species.
The PhD project was initiated in 2007, following consultation between the then recently formed Canberra Indian Myna Action Group (CIMAG), IACRC and the ANU’s Fenner School of Environment and Society, aimed at increasing understanding of the biology of the Indian myna, its impact on other species and the effectiveness of CIMAG’s humane culling program.
The species was deliberately introduced to Canberra between 1968 and 1971, when 110 birds from Sydney were released in the suburb of Forrest.
Since then, Indian myna numbers in Canberra have steadily increased by an estimated 6.4 birds per sq km each year.
By 2006, a mid-range estimate of the ACT population was 93,000.
However, active publicity and humane trapping programs carried out by more than 1300 members of CIMAG have since removed more than 42,000 Indian Mynas from the local environment.
The common Myna was first brought to Australia in 1862 to control insects in market gardens in the city of Melbourne.
The species quickly established in Melbourne and that population became a source population for other introductions in eastern Australia.
In Australia in 2005, the Indian myna was voted in the ABC Wildwatch Australia Survey as the “most significant pest”, “the pest problem seen to be increasing most” and the top “pest problem that needs more control”.
The International Union for the Conservation of Nature has ranked the Indian myna among the world’s top 100 most invasive plants and animals.
Indian mynas thrive in and around human-modified environments, reaching high densities of more than 200 birds per sq km in towns.
Incorporating variables for environmental change in the research model enabled the researchers to obtain a better understanding of the impact of Indian myna establishment on bird abundance.
The model was designed to incorporate changes in species abundance through to habitat modification, thus enabling an understanding of the impact of the Indian myna in a changing environment.
The significance of this Indian myna research is that it is important to understand the impact of an introduced species to provide effective management.
Native bird habitat restoration may be a useful tool to control Indian myna abundance.
However, because of limited resources for management, the ongoing loss of native habitat to urban development and increasing numbers and types of introduced species, there is still much to learn about appropriate management responses for the Indian myna.
Ms Grarock says the research was unable to demonstrate the impact of the Indian myna on threatened species such as the superb parrot (polytelis swainsonii) because limited observations of such species.
“We found no significant negative relationships between Indian myna establishment and the abundance of the galah, eastern rosella, laughing kookaburra, Australian king parrot or the common starling,” says Ms Grarock. “The abundance of the Australian king parrot, eastern rosella and common starling actually appeared to increase after Indian myna establishment.”