St Margaret's Island

St Margaret’s Island lies off the Pembrokeshire coast as a small tidal island north-west of Caldey Island. At low tide it is joined to Caldey by a narrow strip of sand called Little Sound. The island rises to forty metres above the sea and covers seven hectares. Divers often explore the waters around its rocky edges. Little remains of the buildings once used by quarry workers who mined limestone here. The island’s chapel, built probably in the seventeenth century, gave it its name. In the nineteenth century the chapel became housing for quarry workers before the industry closed in 1851. The ruins and a field enclosure are listed by the Royal Commission on Ancient Monuments. Since 1950 the island has been leased from Picton Castle Estate and is managed by The Wildlife Trust of South & West Wales. Cormorants nest on the cliffs in the largest Welsh population, making up three per cent of the British total. Guillemots, razorbills, shags and kittiwakes also breed here alongside several gull species. Puffins use rock fissures but cannot dig burrows because brown rats disturb the ground. Common plants include red fescue, hogweed and sea beet, with sea mallow along the shore.