Dùn is an island in the St Kilda

St Kilda, Scotland

St Kilda is an isolated archipelago west-northwest of North Uist in the North Atlantic Ocean. It contains the westernmost islands of the Outer Hebrides of Scotland. The largest island is Hirta, whose sea cliffs are the highest in the United Kingdom and three other islands , were also used for...

 archipelago. It is nearly a mile long. Its name simply means "fort" in Scottish Gaelic (for more information, see "dun

Dun

Dun is now used both as a generic term for a fort and also for a specific variety of Atlantic roundhouse...

"), but the fort itself has been lost - old maps show it on Gob an Dùin , which is at the seaward end.

Almost joined to Hirta

Hirta

Hirta is the largest island in the St Kilda archipelago, on the western edge of Scotland. The name "Hiort" and "Hirta" have also been applied to the entire archipelago.-Geography:...

 at Ruiaval, the two islands are separated by Caolas an Dùin (the straits of Dùn). This prevents Soay sheep

Soay sheep

The Soay sheep is a primitive breed of domestic sheep descended from a population of feral sheep on the island of Soay in the St. Kilda Archipelago, about from the Western Isles of Scotland...

 from Hirta straying onto the island, and thus it is more vegetated.

The small island is home to the largest colony of fulmar

Fulmar

Fulmars are seabirds of the family Procellariidae. The family consists of two extant species and two that are extinct.-Taxonomy:As members of Procellaridae and then the order Procellariiformes, they share certain traits. First, they have nasal passages that attach to the upper bill called...

s in Britain

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

. Prior to 1828, St Kilda was their only British Isles

British Isles

The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...

 breeding ground, but they have since spread and established colonies elsewhere, such as at Fowlsheugh

Fowlsheugh

Fowlsheugh is a coastal nature reserve in Kincardineshire, northeast Scotland, known for its seventy metre high cliff formations and habitat supporting prolific seabird nesting colonies. Designated as a Site of Special Scientific Interest by Scottish Natural Heritage, the property is owned by the...

.

Dùn, which protects Village Bay on Hirta from the prevailing south-westerly winds, was at one time joined to Hirta by a natural arch. MacLean (1972) suggests that the arch was broken when struck by a galleon

Galleon

A galleon was a large, multi-decked sailing ship used primarily by European states from the 16th to 18th centuries. Whether used for war or commerce, they were generally armed with the demi-culverin type of cannon.-Etymology:...

 fleeing the defeat of the Armada

Spanish Armada

This article refers to the Battle of Gravelines, for the modern navy of Spain, see Spanish NavyThe Spanish Armada was the Spanish fleet that sailed against England under the command of the Duke of Medina Sidonia in 1588, with the intention of overthrowing Elizabeth I of England to stop English...

, but other sources, such as Mitchell (1992), provide the more credible (if less romantic) explanation that the arch was simply swept away by one of the many fierce storms which batter the islands every winter.