LITTLE BUT LETHAL: Tiny wasps save birds from extinction
Gwyneth Perseveranda
Even the smallest forces can protect life on a grand scale, proving that the tiniest actions, sometimes, lead to massive progressions.
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Photo Courtesy of CABI. |
Small parasitoid wasps, known as Microterys nietneri, have extended the lifeline of rare bird species whose survival is threatened by an invasive insect.
The Royal Society for the Protection of Birds (RSP), along with the Centre for Agriculture and Bioscience International (CABI), the Food and Environment Research Agency (FERA), and the Tristan da Cunha Government, resorted to releasing these tiny wasps to eradicate the insects that endanger one of the world's rarest birds, Wilkins' bunting.
Wilkins’ bunting (Nesospiza wilkinsi) is situated on Nightingale Island, part of the Tristan da Cunha, the world’s most remote inhabited archipelago.
They feed on the fruit of the Island cape myrtle, known as Phylica arborea, the island’s only native tree.
The population of these yellow birds are suffering, further worsened by the storms in 2019 that nearly destroyed much of the forest, but before the disaster, only 120 breeding pairs remained.
However, in 2011, the scientists observed an infestation of a scale insect called Brown soft scale (Coccus hesperidum), which had been introduced accidentally by humans.
These scale insects secrete honeydew, leading to the growth of sooty mold that kills the Island cape myrtle.
The arrival of these insects poses threats to destroy the forest and the survival of the Wilkins’ bunting.
“We hadn’t realized quite how damaging the scale insects were on Tristan, affecting many plants as well as Phylica,” said Trevor Glass, head of Tristan Conservation Department.
RSPB, CABI, FERA, and the Tristan Conservation Department targeted these insects by releasing Microterys nietneri, a species of parasitoid wasps specialized in the biological control of brown soft scale.
These wasps took their first release in 2021, facing challenges such as their survivability during transportation in land, sea, and air, along with the enforced stay of a staff, following the safety protocols during the COVID-19 pandemic.
Entomologists found these wasps to be successful in controlling the scale insects, without having any adverse effects on other species in the forest.
The wasps target the scale insects through laying their eggs inside them, eventually leading to the death of the scales as the wasp larvae develop.
Surveys in February 2024 found that there are still an estimated 60-90 pairs of Wilkins’ bunting on Nightingale, despite losing 80% of the forest due to the storm.
Although their population was diminished, the forest displayed signs of recovery since the wasps were released, and scientists believe the number of buntings will have a chance to prosper for the following years.
“This project shows what can be achieved in turning around the fate of a threatened species,” David Kinchin-Smith, the RSPB’s UK overseas territories project manager, said.
“Steely determination, ecological expertise and a large helping of luck have all contributed to the success of this work, but hopefully we, and the wasps, have given the buntings a much-needed lifeline,” Kinchin-Smith added.