Ben Dilley from the FitzPatrick Institute of African Ornithology at the University of Cape Town, is working for the Tristan da Cunha Conservation Department on a two year EU BEST funded project to conserve the forests and birds of Nightingale Island.
In this blog Ben tells us all about the project and why the team is so dedicated to protecting this unique UK Overseas Territory...
Where is Nightingale Island? It’s in the middle of the South Atlantic Ocean and is the smallest (4 km2) of the four islands in the Tristan archipelago.
The main forest area around the ponds on Nightingale.
And buntings live on this tiny island? Yes, there two species of Nesospiza buntings (Canaries) found here and nowhere else in the world: the Nightingale (Nesospiza questi) and Wilkins’ (N. wilkinsi) buntings. The Nightingale bunting (known locally as the ‘Little Canary’) is the smaller species (adults weigh ~25g) with the small narrow bill and it is fairly common and easy to see along the island pathway. The Wilkins bunting (‘Big Canary’) is almost double the size (adults weigh ~50g) and there are only about 85 pairs in the world, all of which live in Nightingale’s Phylica arborea forests, which makes this one of the rarest birds in the world.
The Wilkins’ Buntings are quite secretive and hop around in the undergrowth when not in the canopy.
This sounds similar to Darwin’s Finches at the Galapagos Islands? It really is - the evolutionary radiation is similar in many respects to Darwin’s Finches, except here it’s just two species!
Is most of the island covered in forest? Only about 5% of the island is forested, dominated by beautiful Phylica trees up to around 6m high. The rest of the island is covered with dense tussock grass (Spartina arundinacea) which is about 3-4m high and is very unpleasant to try and walk through!
So why are there so few Wilkins’ buntings? The Wilkins’ bunting has a thick bill which is specialised to crack open fruits of the Phylica trees. Although they also eat invertebrates, they are largely reliant on the Phylica fruits and so their population is limited by the size of the forest (about 10ha or 10 football fields). The other bunting species on the island, the Nightingale bunting, is more of a generalist feeder and eats a variety of seeds and invertebrates and has adapted to breed in both the tussock and forest areas all over the island. Consequently this species is more common on the island with a population of about 4000 pairs.
Wilkins’ Bunting in the forest canopy feeding off the Phylica fruits
What’s this project all about? It’s about conserving a highly specialised and endangered species (Wilkins’ bunting) which is reliant on the relatively small patches of Phylica woodland for their survival. The Tristan da Cunha Conservation Department and the RSPB launched this project with three main aims: (1) to establish new areas of Phylica forests and assess the current health of the Phylica trees; (2) to study the Wilkins’ bunting population (since very little is known about this species); and (3) to improve biosecurity controls.
Left: Delia, Julian, Trevor, Riaan and Kelly with Phylica seedlings in planter trays (photo credit: Graeme Rogers). Right: Trays and pots with Phylica plants in the nursery.
How is the project going? Very well, thanks to the dedicated team of Tristan Islanders who make it all happen!
What are the highlights so far? We have just completed the first field season when we found 49 Wilkins’ nests which was pretty good going. And the first Phylica saplings which were ‘home grown’ from seedlings in our island ‘nursery’ have been planted out as the first of many new pockets of forest which we plan to generate over the next few years.
Left: Two Wilkins’ Bunting eggs in a nest cup lined with Tussock leaves. Right: Wilkins’ Bunting female incubating her eggs.
What could potentially wipe this species out? Probably the biggest threat is the accidental introduction of invasive species - for the buntings, the arrival of rats or mice would potentially be disastrous, as is happening on Tristan da Cunhas Gough Island, where mice are killing seabirds (click here to read more). Part of this project is to develop control measures to reduce the chance of an accidental introduction and an action plan should rodents arrive on the island.
What about the Forests? For the Island Trees (as they are locally known), the main threat we know of is the invasive Greedy Scale insect (Hemiberlesia rapax), which is now widespread across Nightingale and has the potential to decrease the fruit loads of trees – which would be bad news for the Wilkins’ buntings. Some trees are showing local die-off in the canopy, but the impact appears to be minimal at the moment and the Conservation Department are carefully monitoring the trees. Climate change may also affect these forests, as in 2001 when fierce storms wiped out large sections of forest. Another reason to learn how to regenerate the forest sooner rather than later!
A Phylica branch with Greedy scale insects (circled in red).
Look out for our next update in early 2018 after the second season of fieldwork on Nightingale!
From the Bunting team - Ben Dilley, Delia Davies, Trevor Glass, Julian Repetto, George Swain & Kirsty Green.
This project has recieved European Union funding through the BEST 2.0 programme.