skomer and middleholm
Skomer and Middleholm from Wooltack Point Photo: Tara Proud

Skomer, Skokholm and Middleholm hold a special place in the heart of our Biosecurity Officer for Northern Ireland and Wales (Tessa Coledale), following two seasons spent monitoring seabirds on Skomer for the Wildlife Trust of South and West Wales (WTSWW) and the Joint Nature Conservation Committee (JNCC) Seabird Monitoring Programme in 2008 and 2009. This annual monitoring programme has taken place at sample sites around the UK since 1986 and provides data on breeding numbers and breeding success so we can keep an eye on the health of the UK seabird population. As seabirds are top predators this can also be a useful indicator of the state of our seas.

Red sandstoneckiffs Alastair Proud

Red sandstone cliffs on Skokholm Photo: Alastair Proud

Skomer, Skokholm and Middleholm are a group of islands off Martin’s Haven on the Pembrokeshire coast. Skomer and Skokholm are managed by the WTSWW whilst Middleholm is managed by the National Trust. These organisations are working together with the Biosecurity for LIFE project to produce a joint biosecurity plan as these islands are designated within the same Special Protection Area (SPA). Middleholm could provide a bridge for invasive non-native mammalian predators to spread from the mainland to Skomer being only 600m from the mainland and 60m from Skomer.

ManxShearwater RSPBimages ChrisGomersall

Manx shearwater Photo: Chris Gomersall (RSPB-images)

Together these islands are estimated to hold a remarkable 67% of the world population of breeding Manx shearwater. These birds are diurnal but will only come ashore or go out to sea under the cover of darkness and nest underground so you’re unlikely to see them when you visit the islands unless you stay overnight. You will see that the ground is covered in burrows and is therefore extremely fragile so take care to stay on the paths when you visit. Skokholm is also home to the fourth largest storm petrel colony in the UK, holding 8% of the UK breeding population. These birds’ nest in crevices in stone walls or quarries and are also nocturnal when on land to avoid predation. The islands most famous resident however is the puffin, these birds nest underground but come out in the day so you are likely to see rather a lot of them if you visit between April and July. All these ground-nesting species are particularly susceptible to invasive non-native mammalian predators, they would not survive if rats, mink or stoats arrived on the islands.

Puffin LukeHalpin

Puffins on Skomer Photo: Luke Halpin

Dale Sailing have been working with the WTSWW as the sole boat operator to the isles to ensure that biosecurity measures are followed by the 20,000+ visitors who explore the islands each year. The WTSWW has produced some excellent material highlighting the correct way to pack your bag or any food items when travelling to the islands. Bags are checked by Dale Sailing and the wardens before people are allowed to land.

Skomer biosecurity poster

Skomer biosecurity poster Image: WSTSWW

A lot of people think that just because an island has avoided invasive non-native mammalian predators there is no chance of a future incursion. Did you know however that rangers in New Zealand have found mice in the rucksacks of unsuspecting tourists visiting protected seabird islands and we know of instances over here where even a rat has been found being carried in a rucksack of an unsuspecting conservationist after they put it down momentarily, open with their lunch exposed! Just remember that rats have reached about 80% of the world’s islands and that all it takes is for one pregnant female to reach a seabird island to cause chaos. This did in fact happen on Skomer in the early 20th century but luckily the stowaway was quickly captured. So please don’t forget to pack on the day of travel, check your bags for signs of stowaways and don’t leave your luggage unattended. We can all do our bit to keep these wildlife paradises safe.

On the approach to Middleholm James Roden

On the approach to Middleholm Photo: James Roden

You can’t normally visit Middleholm due to its inaccessibility and fragile ground. Under normal circumstances you can visit Skomer and Skokholm but this summer due to Covid-19 the islands are shut.

To keep up to date with what the stranded island wardens are up to on Skomer and Skokholm you can follow their blogs:



October 2020

St Agnes and Gugh, Isles of Scilly

The Isles of Scilly are home to our Biosecurity Officer, Northern Ireland, Wales and SW England (Jaclyn Pearson). The inhabited islands of St Agnes and Gugh in particular are very special for seabirds. Here, brown rats were removed in 2013 to protect species including Manx shearwaters and storm petrels and the results have been incredible, not just for wildlife but for the community too. Together the 85 residents of St Agnes and Gugh continue to carry out rodent biosecurity with the support of RSPB and Isles of Scilly Wildlife Trust.

March 2020


Grassholm is one of those islands that assaults your senses upon approach with both the smell, noise and sight of over 36,000 pairs of gannets. On a round island boat trip you’ll see them on their nests or flying overhead like aeroplanes before folding their wings back and diving at speed to catch their prey in the surrounding waters. 6.8% of the world population of Northern gannets breed on this lump of rock just 10 hectares in size. In fact, the majority of the island is now white in colour due to the animals and their guano, with only a relatively small strip of grass remaining where they are yet to colonise. Grassholm is the third largest gannetry in the UK after the Bass Rock and St Kilda – two other sites we’re also working on.

March 2020

The Farne Islands

Lying only a mile off the Northumberland Coast, the Farne Islands archipelago hosts one of England’s most impressive seabird colonies, managed by the National Trust. Depending of the state of the tide, the Farnes boast between 15 and 28 islands, the largest being just 16 acres in size. Onto these small isles, an assemblage of over 160,000 seabirds crowd together each summer to breed.

Illustration of birds

Contact Us

If you’d like more information or would like to report a sighting of an invasive predator please contact us using the form below: