|Area||10.72 ha (26.5 acres)|
|Highest elevation||42 m (138 ft)|
|Community||Marloes and St Brides|
Grassholm (Welsh: Gwales or Ynys Gwales) or Grassholm Island is a small uninhabited island situated 13 kilometres (8 mi) off the southwestern Pembrokeshire coast in Wales, lying west of Skomer, in the community of Marloes and St Brides. It is the westernmost point in Wales other than the isolated rocks on which the Smalls Lighthouse stands. Grassholm is known for its huge colony of northern gannets; the island has been owned since 1947 by the Royal Society for the Protection of Birds, and is one of its oldest reserves. It reaches 42 metres (138 ft).
Grassholm National Nature Reserve is the third most important site for gannets in the world, after two sites in Scotland: St Kilda and Bass Rock. It serves as a breeding site for 39,000 pairs of the birds, and supports around 10 percent of the world population. The turbulent sea around Grassholm is a good feeding area for porpoises and bottlenose dolphins.
The island has a significant problem with marine plastic, brought to the island by breeding gannets, as nesting material which the birds have mistaken for seaweed floating in the surrounding waters. The problem has been ongoing through twelve years of RSPB conservation to 2017, and surveys have indicated that 80% of nests contain waste plastics.
Geologically, the island is largely formed from keratophyre, though the northwest coast and the islet of West Tump are formed from basalt. A couple of NE-SW aligned faults cross the island. Raised beaches are present in places.
The entertaining of the noble head
Grassholm has been identified with Gwales, an island in the medieval Welsh story Branwen ferch Llŷr (Branwen the daughter of Llŷr), one of the Four Branches of the Mabinogi. Gwales is the site of a fabulous castle where the severed head of Brân the Blessed is kept miraculously alive for eighty years while his companions feast in blissful forgetfulness, until the opening of a forbidden door that faces Cornwall recalls them to their sorrow and the need to bury the head at the White Mount (the Tower of London). Brân is the Welsh for 'raven', which has a legendary connection with the Tower of London.
And at the close of the seventh year they went forth to Gwales in Penvro. And there they found a fair and regal spot overlooking the ocean; and a spacious hall was therein. [...] And that night they regaled themselves and were joyful. [...] And there they remained fourscore years, unconscious of having ever spent a time more joyous and mirthful. And they were not more weary than when first they came, neither did they, any of them, know the time they had been there. And it was not more irksome to them having the head with them, than if Bendigeid Vran had been with them himself. And because of these fourscore years, it was called "the Entertaining of the noble Head."
- "SPA Description - Grassholm". Joint Nature Conservation Committee. DEFRA. Retrieved 2 March 2017.
- "Grassholm Island". Ordnance Survey. Retrieved 7 February 2019.
- Ordnance Survey. "SM5909". Geograph. Retrieved 16 November 2018. (click on map)
- Anon. "Grassholm". RSPB wepages. The Royal Society for the Protection of Birds. Retrieved 11 April 2010.
- "Visit Pembrokeshire: Grassholm". Retrieved 8 November 2018.
- "Saving the birds ensnared on 'plastic island'". Euronews. 20 October 2017. Retrieved 20 October 2017.
- "Gannets ensnared by twisted plastic around their legs on Grassholm island". Sky News. 20 October 2017. Retrieved 20 October 2017.
- "Plastic Gannets". Autumnwatch. 19 November 2014. BBC. BBC2. Retrieved 20 October 2017.
- British Geological Survey 1978 1:50,000 scale geological map sheet (England and Wales) 226/227 Milford (Keyworth, Notts)
- "Branwen ferch Lyr: The Second Branch of the Mabinogi". www.mabinogi.net.
- The Mabinogion: Branwen the Daughter of Llyr, translated by Lady Charlotte Guest. Online at www.sacred-texts.com.
- Newstead, Professor Helaine H., Bran the Blessed in Arthurian Romance pub. Columbia University Press 1939.
- Mitchell, W H, and Sawyer, L A (1995). The Empire Ships. London, New York, Hamburg, Hong Kong: Lloyd's of London Press Ltd. ISBN 1-85044-275-4.
- "History". Angle Lifeboat Station. Retrieved 30 May 2010.
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