Charles Sturt University, Media Release, 18 August 2023
Researchers at Charles Sturt University are preparing to visit Lord Howe Island for the last time as part of a study on the impacts of a rodent eradication project on two native bird species.
The study, ‘Effects of an island-wide rodent eradication programme on two threatened bird species’, was recently published after years of research both on and off the island.
During National Science Week (Saturday 12 to Sunday 20 August), Albury-Wodonga-based researcher and Associate Professor in Ecology/Ornithology Melanie Massaro in the Charles Sturt University Gulbali Institute of Agriculture, Water and Environment said studies like this are vital to quantify the benefits and costs of large-scale conservation interventions.
“For the past 50 years, rodent eradications have been conducted worldwide to reverse the devastating impacts of introduced rodents on island species,” she said.
“This study investigated the effects of a rodent eradication on Lord Howe Island on two native birds.”
Published in Pacific Conservation Biology (Segal RD et al. (May, 2022) doi:10.1071/PC21068), the study is one of few that quantitatively assessed the ecological effects of an island-wide rodent eradication on native birds, including one terrestrial bird species, using pre-and post-eradication data.
Professor Massaro said to mitigate the risk of Lord Howe currawongs being poisoned during baiting operations, 30 – 40 per cent of the population were taken into captivity during baiting, while the remaining currawongs were left in the wild.
“We studied currawong survival, nesting density and breeding success pre-and post-eradication to test how the baiting, a period in captivity, and the removal of rodents affected currawongs,” she said.
“We also investigated breeding success of white terns as they were expected to benefit from the eradication due to predator reduction.”
Professor Massaro said the researchers found that many currawongs left in the wild disappeared during the baiting period and nesting densities in one part of the island were significantly lower after the eradication.
“These currawongs likely died of poisoning as they were not resighted for two years post-eradication,” she said.
“White tern breeding success did not increase after the rodent eradication, although their predators were largely eliminated.”
Researchers, however, found that captive management of currawongs mitigated the adverse effects of the baiting.
“As those currawongs that survived had high breeding success, we predicted that the population will soon recover to pre-eradication size,” Professor Massaro said.
“Our recent visits to Lord Howe Island confirmed that the currawong population has recovered.”
The recent visit also revealed the Lord Howe Woodhen population had increased six-fold from approximately 200 birds pre-eradication to 1200 birds during the latest count.
Professor Massaro said that as well as informing stakeholders and demonstrating a return on investment for funding bodies, measuring the ecological benefits and consequences of rodent eradications may contribute to the planning and management of future eradications.
“Results of this study highlight the importance of carefully planned and executed captive management of threatened native species and the necessity of integrating ecological monitoring as part of future rodent eradications on islands,” she said.
Professor Massaro will visit Lord Howe Island later this year for a final re-count of currawongs as part of the study.
