The Shiant Isles are one of the most important breeding colonies for seabirds in Europe - around 10 per cent of UK puffins and 7 per cent of UK razorbills breed here every year. However, when the project began in 2014, as well as these amazing seabird populations, the islands were also home to a population of invasive non-native black rats.
Black rats were thought to have arrived on the Shiant Isles from an 18th century shipwreck and had colonised the three main islands in the archipelago. In April 2012 a survey estimated there were around 3,600 rats on the islands - this number was thought to increase significantly in the summer months when more food was available.
The non-native black rats were known to predate on seabirds' eggs and chicks on the islands. Their presence was considered to be impacting the breeding success of ground nesting species and discouraging other species like Manx shearwaters and European storm petrels from colonising.
The four core objectives of the project were to:
In March 2018 the Shiants were declared officially free of black rats as a result of the project and in September 2018 the first storm petrel chick in recorded history was heard calling from a nest crevice on the islands, a sound that the project team had been hoping to hear since the eradication was completed.
The rat eradication took place during winter 2015-2016 when rat numbers were at their lowest due to limited food availability, and when seabirds were not on the islands. Led by Wildlife Management International Limited, which has had successes with similar projects around the world, the eradication operation was carried out using rodenticide distributed in bait stations set in a grid across each of the Shiant Isles, including the sea stacks. This took more than four months to complete. Special measures were put in place to ensure that this phase of the project did not impact on the wildlife on the islands over the winter.
The decline of black rats, which are not native to the UK, can be attributed to the arrival of brown rats which are larger and can outcompete them. Since the eradication of black rats from Lundy, there were claims that the Shiant Isles had the only remaining UK population. This is not the case.
Although black rats are rare in the UK, evidence demonstrates that populations survive on other islands and in localised areas of the British mainland. Recent National Biodiversity Network data show populations around the UK, particularly in ports and port towns. This is supported by anecdotal records from London and Liverpool.
Globally, black rats are invasive and remain common and widespread throughout their historic natural range in Asia, where the population is stable and faces no known threat to its conservation status. The species is also common in large areas of the world where it has been introduced and successfully colonised.
As well as bringing Manx shearwaters and storm petrels to the Shiant Isles, this project also aimed to build UK expertise in island restoration, particularly biosecurity, to minimise the risk of future accidental introductions of invasive species to seabird islands. As part of this work, best practice guidance and training courses on biosecurity for seabird islands were developed at the Shiants. The biosecurity measures for the Shiants were promoted to island visitors and boat operators to ensure they remain rat free. The project has paved the way for future island restoration projects to take place around Scotland and help the internationally important seabird populations.
The dramatic Shiant Isles rise up from the sea around five miles east of Harris in the Hebrides. Their name derives from the Gaelic Na h-Eileanan Seunta meaning "holy" or "enchanted" isles. This tiny cluster of islands is one of the most important seabird breeding sites in Europe and is classified as a Special Protection Area (SPA) under the EU Wild Birds Directive.
In the seas around the UK, breeding seabird populations are not considered to be in good condition. In more than a third of species, breeding abundance is 20-30 per cent lower than in the 1990s. There have also been frequent widespread breeding failures in recent years in up to a third of breeding seabird species. Lower availability of small fish, on which the seabirds feed, has been largely responsible. Climate change is likely to be driving these reductions in food availability, but impacts from human activities cannot be ruled out. Scotland and the UK have a global responsibility for these species; 80 per cent of the world's Manx shearwaters breed around UK shores.
The reasons for these declines are complex and in many cases are related to changes in their prey. However, invasive non-native species, like black rats, can have significant impacts on seabird species' ability to breed and in many cases make islands uninhabitable for seabirds. The project partners are committed to doing everything they can to protect and restore seabird populations and this project is part of that commitment.
Prior to the project beginning at the peak of the breeding season the Shiant Isles were home to hundreds of thousands of seabirds including 10 per cent of the UK population of puffins and 7 per cent of the UK population of razorbills. It is hoped that many more will be able to breed successfully here following the islands' restoration.
The Shiant Isles are one of the most important seabird breeding sites in Europe and are classified as a Special Protection Area (SPA) under the EU Wild Birds Directive. The most recent assessment in 2015 has shown that some seabird species on the Shiants are in unfavourable condition. This includes shag and guillemot as well as some cliff nesting species such as kittiwake and fulmar. There is also evidence that suggests the puffin colony used to be more extensive.
It is likely that black rat predation led to the loss of breeding storm petrels and Manx shearwaters from the islands and added to other pressures on breeding seabirds such as pollution and food shortages. By eradicating black rats and improving biosecurity, this project has removed this pressure on vulnerable seabirds, and allowed storm petrels to return to the Shiants. The Shiants are now a much safer place for seabirds, ensuring that the islands continue to be a safe place for them to breed and successfully raise chicks.
Now that black rats have been successfully removed from the Shiants, the future challenge is to keep these islands free of rats and other rodents in perpetuity. Following the completion of the project, the partners have committed to continue to work together to carry out regular biosecurity monitoring and to promote biosecurity measures to island visitors to ensure that rats do not reach the Shiants again. An incursion response team has been established so that if rodents are detected, they can be removed quickly before a population becomes re-established. Annual monitoring will also be undertaken to document the recovery of key seabird species and colonisation of the islands by storm petrels. This work will be supported by the Shiants Auk Ringing Group which has been studying seabirds at the islands since the 1970s.
A biosecurity audit of the UK wide network of Seabird Special Protection Areas (SPAs) that was carried out as part of this project identified that there was a lack of awareness around biosecurity. The information from this work and the momentum gained through biosecurity training events held during the project helped to inform the development of a UK wide Biosecurity for LIFE project which started in August 2018.
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