St Margaret's Island

The island derives its modern (English) name from a chapel that was built there, probably in the 17th century.

In Victorian times the chapel was converted into housing for local quarry workers, who mined limestone on the island, which was abandoned by 1851.

[4][2] The chapel ruins and a field enclosure are recorded by the Royal Commission on Ancient monuments.

[2] St Margaret's Island is a sensitive conservation site because of the birds that nest on its cliffs: cormorants (the largest population of this species in Wales, constituting 3% of the total British population), guillemots, razorbills, shags, kittiwakes, great black-backed gulls, lesser black-backed gulls and herring gulls.

Puffins breed in rock fissures, but the existence of brown rats prevents burrow nests.