Grassholm Photo: David Wootton (RSPB-images)
Grassholm from the air Photo: David Wootton (RSPB-images)

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.

Flying gannet Grassholm Credit L Morgan

Flying gannet Photo: Lisa Morgan

Grassholm is the oldest RSPB reserve in Wales having been managed by the organisation since 1948. Then it was home to just 7,000 pairs of gannet but gannet are one of the few seabird success stories with populations increasing around the UK. This is not a reason to be complacent about their protection as they nest at just 18 sites around the UK, 16 of which are in Scotland with Grassholm being the only colony in Wales and Bempton Cliffs being the only colony in England. The species doesn’t breed in Northern Ireland.

Gannets RSPBimages AndyHay

Pair of Gannets Photo: Andy Hay (RSPB-images)

Grassholm is over 15km from the Welsh mainland which offers it some protection from invasive non-native mammalian predators as they are unlikely to swim there. The island is uninhabited and doesn’t allow landings due to the disturbance on the colony. Researchers and wardens land between 3 – 5 times from July to October to monitor the gannets, carry out biosecurity checks and later in the season to release any fledglings or adults trapped in the plastic waste that is found in a shocking 80% of nests on the island.

Small chick in plastic nest Credit Lisa Morgan

Gannet chick in nest containing plastic Photo: Lisa Morgan

We must remain vigilant with biosecurity though as shown by an incident before Christmas when a container ship lost some of its cargo during a storm just 1km from Grassholm. A lot of apples, ricecakes and plastic containers were washed up on the coast around Pembrokeshire but thankfully none have been detected on Grassholm itself. Invasive non-native mammalian predators such as rats and mice are high risk stowaways and can float on storm debris to nearby islands. Remember all it takes is one pregnant female to cause chaos on a seabird island!

Grassholm   Credit L Morgan

Gannets nesting on Grassholm Photo: Lisa Morgan

We’re working with the RSPB site managers to assess their existing biosecurity measures and to help provide resources so they’re able to carry out a biosecurity check in February/March each year before the gannets return to Grassholm.



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.

April 2020

Skokholm, Skomer and Middleholm

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.

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

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