Nightingale Island is the smallest of the 4 islands that make up the Tristan archipelago. It is home to millions of breeding seabirds, and two endemic land birds, including the Wilkins’ bunting (Nesospiza wilkinsi), which is listed as Endangered in the IUCN Red List.
Only 80 pairs of Wilkins’ bunting breed on Nightingale but estimates of basic demographic parameters such as productivity and survival are limited. The persistence of the species is threatened by the small population size, their sensitivity to habitat loss, and the potential for accidental introductions of predators.
Wilkins bunting in Phylica tree.
The adults are found primarily in the Phylica woodland, which now only grows at the top of the island in fragmented remnants of a few hectares, and feed primarily on the Phylica seeds. Without the Phylica woodland, this highly specialised and endangered species would likely suffer serious declines, and potential extinction.
A number of immediate and potential threats are of concern including the introduction of invasive rodents and other alien species from nearby Tristan da Cunha or shipwrecks. A major biosecurity concern is a sooty mould fungus (Seiridium phylicae) which influences the seed-set of Phylica trees. This sooty mould is common on both Tristan and Inaccessible islands. The arrival of this fungus on Nightingale could have catastrophic effects on the Wilkins’ buntings if the Phylica tree, as both their food source and primary nesting habitat is negatively affected.
Description of the project
The project aimed to strengthen inter-island biosecurity measures to prevent the arrival of this fungus and other non-native species to Nightingale on human visitors moving between the islands.
The Wilkin’s buntings territory was mapped and the population was studied to determine its growth rate and estimate the reproductive success. Restoration of Phylica woodland was undertaken by planting collected seeds and transplanting saplings from existing stands.
The project also developed a biosecurity protocol for visitors to Nightingale Island and established a monitoring protocol for new weeds along commonly travelled routes on the island. The Phylica stands will be monitored annually to check for signs of sooty mould fungus and introduced scale insects.
Above from right to left: Riaan, Julian and Graeme building the Phylica Nursery; Phylica plants in the completed nursery; and Graeme Rogers’ photo shows Delia Davies, Julian Repetto, Trevor Glass, Riaan Repetto and Kelly Swain with Phylica seedlings in planter trays
Main Achievement :
Two summer field seasons on Nightingale Island led to increased knowledge of the breeding biology and a better population estimate of the endemic Wilkin’s bunting, Nesospiza wilkinsi.
A nursery area of Phylica trees was planted on Nightingale Island. Eighty percent of propagated plants that were planted out, were alive and well during the second monitoring season. The project has allowed lessons to be learned on best practices to maintain this nursery in the long term.
The staff at Tristan Conservation Department have increased understanding of the demography and ecology of the Wilkins’ Bunting and the response of the population to the recreation of Phylica habitat. They can also identify and assess the health of the Phylica trees, identify, locate and monitor different scale insect species, as well as finding and identifying bunting nests.
Biosecurity is improved through the adoption of a Biosecurity Protocol and establishment of effective monitoring thereby decreasing the potential for invasive species to arrive on Nightingale island.
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