What is ‘special’ about The Skerries SSSI?

The Skerries has 2 special features:

As well as the features listed above, The Skerries has other habitats that contribute to the special interest. These include maritime grassland, characterised by common scurvey-grass, lesser sea-spurrey, red fescue and common sorrel, inter-tidal rocks and pools and low maritime cliff with associated ledges and crevices. Of particular interest are species-rich sediment-floored rockpools and the small cushion star. This diversity of habitats supports other species including a breeding bird assemblage (arctic tern, common tern, oystercatcher, lesser black-backed gull, greater black-backed gull, puffin, herring Gull, shag, rock pipit), breeding and visiting grey seals, and these too are a key component of the special interest of the site. Unless specified below, management of this site should aim to look after these habitats and species as well as the listed features of interest.

What do we want The Skerries to look like?

The site should contribute to the network of tern breeding sites within the Irish Sea and more locally along the coast of Anglesey. Its integrity as a breeding site for all tern species should be maintained, primarily by keeping it free from mammalian predators and minimising avian predators. This should occur even in years when one or more of the nesting species fails to be present. The integrity of the tern colony is dependant upon off-site factors, such as availability of food, the presence of alternative nesting sites in adverse years within the Irish Sea and the integrity of their winter migration sites.

The site should provide the opportunity for roseate terns to nest. As they tend to nest in established tern colonies, usually associated with common terns, the maintenance of a viable common and arctic tern colony is imperative.

The presence of the other breeding bird species should be maintained. However as nesting terns can suffer predation from nesting gulls, it is essential that the two colonies be protected from conflict. Breeding and immature gulls can be particularly successful predators of tern colonies. Even if separation between the gull and tern population is achieved, it may be necessary to control individuals that are exerting particularly severe predation pressure.

The island’s grey seal colony could be adversely affected by disturbance during autumn pupping and should be protected from excessive human disturbance during this period.

What management is needed on The Skerries SSSI and why?

Although The Skerries is an excellent place for wildlife it will only remain so if the necessary management continues. CCW’s aim is to work with you to ensure that this management is carried out.

What does this mean in practice?

There are many factors that could damage the special features at The Skerries if they are not properly managed. These are the ones we regard as most important:

Competition for Nest Space: Expansion of the area occupied by breeding gulls has the potential to significantly reduce the viability of the tern colony through direct occupation of nesting areas. Management of the gull colony (by removing gull nests and / or eggs within a specified exclusion area around the core tern breeding colony) may be necessary to maintain a viable tern nesting area.

Disturbance: Nesting terns and breeding grey seals are susceptible to high levels of disturbance. Significant disturbance is not currently known to occur during the critical autumn period for grey seals. During the tern-breeding season (May – Aug) there is potential for significant human disturbance from casual visitors (who access the islands by boat, canoe and jet ski) and by Trinity House staff and contractors. Control of disturbance during this period is likely to be critical in ensuring the integrity of the tern colony. At present, controls are implemented via Trinity House’s “No Landing” policy and by seasonal wardens employed by the RSPB. The disturbance caused by predators (especially peregrines) may also be significant.

Predator control: Predation is a natural phenomenon of nesting bird colonies. However, the fragility of the tern colony, (given the paucity of other available nest sites), may mean that predation needs to be limited. The main predators are the gull species, which cohabit the island. To minimise predation, gulls should be prevented from nesting within, or close to, the tern colony. Wardening throughout the nesting season also assists in preventing predation from other bird species. Mammalian predators (particularly rats), not currently present on the islands, are a significant potential threat. Provision of nest boxes or shelters may help reduce predation of terns by other species.

Providing appropriate nest sites: Roseate terns regularly nest in holes and hollows, including nest boxes. In order to provide greater nesting opportunities for roseate terns, nest boxes may be placed within the colony prior to occupation each year.

There are a number of off-site factors that have the potential to significantly impact on the features of this site. These factors are highlighted below

Food supply: Nesting terns require a regular supply of food (sandeels and other small pelagic fish) available to foraging birds within a short distance of the colony. Any actions or events likely to impinge on this resource should be resisted.

Alternative Sites: The Skerries is one of a suite of sites around Anglesey and other parts of the Irish Sea (including Rockabill island and Lady’s Island Lake in Ireland), which are used by nesting terns. Former sites such as Rhoscolyn Beacon and Ynys Gorad Goch may be re-occupied in the future. Actions or events likely to affect the availability of these alternative sites should be addressed through appropriate mechanisms.

Wintering territory: Terns are migratory birds and spend most of their lives away from the nesting colony. Actions or events likely to impinge on the sustainability of the population should be addressed through appropriate mechanisms.


Our knowledge of wildlife is far from complete. It is possible that new features of value may appear and new management issues may arise in the future, whilst other issues may disappear. This statement is written with the best information we have now, but may have to change in the future as our understanding improves. Any information you can provide on the wildlife of your site, its management and its conservation would be much appreciated.

If you would like to discuss any aspect of your SSSI, or have any concerns about your SSSI, please contact your local CCW office.

Your local office is;

Cyngor Cefn Gwlad Cymru/Countryside Council for Wales

North Region

Llys y Bont,

Ffordd y Parc,

Parc Menai,


Gwynedd, LL57 4BN,

Telephone: 01248 672500

Fax: 01248 679259