The uninhabited Puffin Island, off the eastern tip of Anglesey, is itself the ninth largest coastal island in Wales, 28 ha in area and rising to 58 m asl. It looks much smaller in this image.

The English name is derived from the large colonies of Puffins which once occupied the island and which were exploited as a food source until the 19th Century. However, thoughout my childhood, seeing the island on the horizon whilst passing on family holidays to Anglesey and the Lleyn peninsula, I knew it as 'Rat Island', as it was well-known that Brown Rats, accidentally introduced in the 19th Century, had virtually eliminated the Puffin population (~40 birds in the 1890s, from a peak of ~4,000). The rats were in turn eradicated in a 1998 poisoning programme, and the island is now designated a Special Protection Area for its colonies of sea birds including Cormorants and, yes, Puffins. It's not publicly-accessible.

The Welsh name, meaning 'Seiriol's Island', refers to the 8th Century saint who established a small religious community on the island at the same time as he founded the monastery nearby on 'mainland' Anglesey, which became Penmon Priory (see foregoing photos). St. Seiriol is said to have been buried on the island.