Miner offences

Farzaneh Etezadifar is using genetics to discover why noisy miners have recently become such a nuisance, and how we can aid management efforts.

 
 Illustration by Leigh Douglas

Illustration by Leigh Douglas

 
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Ethograms is a monthly column published in collaboration with the Australasian Society for the Study of Animal Behaviour (ASSAB), showcasing the work of early-career researchers. Dominique Potvin is a lecturer at the University of the Sunshine Coast, and an outreach officer for ASSAB.

Managing pests is an important part of environmental conservation. We in Australia are well aware of the efforts to control invasive introduced species such as cane toads or rabbits — two so-called ‘wars’ that have been waged for decades. Recently, however, a different kind of pest has been identified, in the unassuming form of a native honeyeater.

The noisy miner is an Australian songbird that thrives in patchy, degraded woodland, a habitat type that has become commonplace in and around human habitation. As their numbers have increased, scientists are finding that many smaller bush birds are being driven out. The problem is so severe that the noisy miner has now been nominated as a Key Threatening Process under the national Environment Protection and Biodiversity Conservation (EPBC) Act. Even the Indian myna — a similar looking, introduced pest species — can’t compete with the native miners, which are having a devastating effect on entire ecosystems.

Over the past three years, a joint project between the Australian Museum, University of Queensland, University of Wollongong and University of New England has attempted to restore biodiversity in certain regions of New South Wales through sanctioned and controlled culls of noisy miners. Amazingly, the miners recolonised cleared sites almost immediately after the cull — some within 24 hours — demonstrating a resilience and population structure that far surpassed scientists’ expectations. Other sites have seen longer-term reductions in miner populations, although it’s unclear why some colonies stabilise at lower population levels and others repopulate almost instantaneously.

 
  Noisy miners thrive in woodland habitats that have undergone human disturbance, and this poses a problem to other native birds.  © Paul McDonald

Noisy miners thrive in woodland habitats that have undergone human disturbance, and this poses a problem to other native birds. © Paul McDonald

 

To understand how noisy miner colonies can achieve such a feat, PhD candidate Farzaneh Etezadifar, from the University of New England, has been the recipient of all the miner carcasses from these experimental culls. Extracting and analysing DNA from these birds will allow her to determine the colonies’ sex ratio and social structure, and how the birds are related to each other. She can then combine these data with behavioural observations to identify which birds are the main culprits responsible for ousting other species from miner-dominated areas. Bold or aggressive behaviours, such as mobbing, are generally considered a colony defence mechanism, but may only be characteristic of a few individuals. If this is the case, then colony-level removal may not be necessary or particularly effective.

“Understanding population dynamics, gene flow and the way that relatedness underpins successful noisy miner colony structure across fragmented woodlands is an important research priority,” says Etezadifar.

 
   A noisy miner in a wild study population (left), and PhD researcher Farzaneh Etezadifar with the victims from an experimental miner cull (right).  © Paul McDonald; © Amrit Kaur

 A noisy miner in a wild study population (left), and PhD researcher Farzaneh Etezadifar with the victims from an experimental miner cull (right). © Paul McDonald; © Amrit Kaur

 

Noisy miners present a rare case in conservation: They are native to Australia, but also pose an invasive threat to previously miner-less habitats, mainly due to human landscape modifications. Since native fauna is protected under Australian law by default, the issue of conservation and management of problematic native species can be tricky to navigate. Etezadifar says that the results of this study will lead to more effective and efficient noisy miner control methods. This, in turn, will help direct efforts towards ethically rebalancing bird communities and even entire ecosystems.

The project is still in its early stages, and Etezadifar is spending many days in the laboratory, trying to measure, analyse and extract high-quality DNA from hundreds of carcasses. “The massive sample size can be a challenge and an advantage to my study at the same time,” she says.

Despite the mountain of work ahead of her, Etezadifar is excited to be working on research that combines behavioural ecology, zoology and genetics to solve a complex conservation issue. It is a great example of how we can use basic science to inform management approaches. Eventually, it may even lead us away from ‘waging war’ on pests, and towards more peaceful means of biodiversity restoration.

Edited by Andrew Katsis