Isles of Scilly Seabird Recovery Project

St Helen's restoration (rat clearance) winter 2023/2024

This winter, IoSWT and partners will be protecting the breeding seabirds on St Helen’s by clearing the island of rats (rats were eradicated from St Agnes and Gugh in 2013/2014 and from Round Island in 2021/2022). You may see team members working and bamboo canes with flagging tape marking bait stations at every 50m.

For residents who visit St Helen’s in winter please do not take your dog(s), as although the toxic bait is in stations, a rat could drop bait outside a station. There will be a sign on the island that explains the use of toxic rat bait, and trail cameras will be on the island from November 2023 to March 2024. If you have any concerns, please contact the vet or doctor immediately.

Why is the partnership clearing rats from St Helen's this winter?

• To safeguard the breeding colonies of Manx shearwaters and puffins on St Helen’s and reduce the likelihood of rats swimming to nearby Round Island (cleared of rats in 2021/2022, as it is the second most important island for breeding Manx shearwaters and storm petrels on Scilly). Routine checks of Round Island are conducted as part of the project to detect early signs of reinvasion from rats, during a recent check in late 2023 rat signs were discovered. The clearance project has now been extended in range to include Round Island.
• To act as a pilot project to trial and develop techniques and materials to be used in potential future eradication projects, which would include Bryher, St Martin’s, Tresco and uninhabited islands.
• To learn more about carrying out this work in winter, on uninhabited islands without quays.

There is a likelihood that rats, over time, will return to St Helen’s, swimming from Tresco or St Martin’s. Therefore, this project is not called a rat eradication project (as St Agnes and Gugh was, and as a future larger project would be), it is instead termed a rat clearance project which will have learning outcomes to help future planning.

The Isles of Scilly Seabird Recovery Project 2013-2017

The Isles of Scilly Seabird Recovery Project (IOSSRP) was successful, with St Agnes and Gugh declared rat-free in early 2017, however biosecurity actions to prevent the return of rats are still imperative. This is still the largest community-based successful island restoration project in the world to date.

IOSSRP set out to reverse recent declines in seabird populations on the Isles of Scilly through removal of non-native species (brown rats) from the islands of St Agnes and Gugh, and maintaining Annet and associated uninhabited islands as rat-free. It enabled people living on and visiting the Isles of Scilly to learn about, take pride in, and play an active role in celebrating and conserving their seabird heritage. It also trained and supported island communities to embrace the benefits of the seabird recovery and continue to protect their heritage once the project has ended.

Rats were also discovered on Round Island January 2022 through the work of Biosec for Life. As Round Island is important for breeding storm petrels and Manx shearwater, the RSPB and partners including the Isles of Scilly Wildlife Trust, Trinity House, Duchy of Cornwall, AONB and Natural England removed the rats with local volunteers between January and April 2022. We believe that this was successful but a two-year period is required before the island can be declared rat-free.

The IOSSRP reformed in 2022 and confirmed that rats remained largest threat to burrow-nesting seabirds on land, so the feasibility of rat eradication is now being revisited on some of the other islands.

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Helping seabirds on Scilly

The latest project proposals include removing rats from three inhabited islands – Bryher, Tresco and St Martin’s, as well as up to 35 uninhabited islands nearby. The proposals are still very much at the planning stage but we envisage the project will be a partnership between Isles of Scilly Wildlife Trust, RSPB, Natural England, Duchy of Cornwall, the Isles of Scilly Area of Outstanding Natural Beauty (AONB) and representatives from Bryher, St Martin’s and Tresco Estate.

Rats are known to have very detrimental effects on seabird populations through predation and competition for food and habitat. Their removal quickly leads to benefits for seabird populations, notably increased seabird numbers. On St Agnes and Gugh, Manx shearwaters were recorded successfully breeding within one year of the eradication and over 80 pairs were recorded in 2022 compared to 22 pairs and no fledged chicks in 2013. European storm petrels were first recorded returning to St Agnes in 2015, with 9 pairs in 2016.

Manx shearwaters on Ramsey and Lundy Islands have increased nearly tenfold in the 15 years since the eradication of brown and black rats and the recolonization of European storm petrels and other small burrowing seabird species has been recorded after long absences.

Seabird successes

Seabird populations in Scilly are important but also vulnerable and face a variety of threats. On land the biggest threat is predation of eggs and chicks by brown rats. The overall population of seabirds declined by 31.3% between 1983 and 2015/16. Historically the population of seabirds was in the hundreds of thousands but has now declined to just 15,994 birds (7,997 pairs). To help the islands’ seabird populations meet future challenges opportunities to improve their current conservation status and breeding range need to be addressed.

The new project seeks to build on the success of nearby St Agnes and Gugh which became rat free in 2016 and saw seabirds returning within a year and chicks fledging for the first time in decades. Further work is required to maintain the islands as seabird friendly and with the support of the local community, the Wildlife Trust now has the same ambition for the inhabited islands of Bryher, St Martins and Tresco.

As with the successful removal of rats from St Agnes and Gugh, the proposed project would take part during a six-month period of the winter and a fundraising plan would be needed.

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