Western Rocks

Also within

Cornwall County Isles Of Scilly Scenic Area

Condition (Natural England)

Geology & landscape

Rock Type: Granite

Landscape processes: Volcanic / Igneous

Birds & fish recorded

Birds

Description

Area, 62.7 ha154.9 ac Description The Western Rocks lie on the western edge of the Isles of Scilly archipelago between Annet and Bishop Rock. They comprise a series of small uninhabited granite islands, including great Crebawethan, Rosevear, Rosevean, Gorregan, Melledgan and Hellweathers, together with numerous other isolated rocks and ledges. All of the islands are lowlying, reaching a maximum height of only 17 metres on Rosevean and hence they are all exposed to the full force of the Atlantic south west gales and excessive salt spray. Shallow skeletal soils are mainly confined to the larger islands; elsewhere soils are only found in isolated pockets in the granite. These thin soils and the extreme exposure severely limit the vegetation and only five species of vascular plant have been recorded. All five species are found on Rosevear where tree mallow Malva arborea occurs in abundance, together with sea beet Beta vulgaris sp maritima, common scurvy grass Cochlearia officinalis, rock sea spurrey Spergularia rupicola and orache Atriplex sp. Some of the other islands and rocks including great Crebawethan are often completely devoid of flowering plants. The Western Rocks are of particular importance as a sea bird colony supporting some 11 species of breeding sea birds. The breeding colony of shag Phalacrocorax aristotelis is of national importance; it is also the largest colony of this species in the archipelago, with the colony on Rosevear being of particular note. The island of Gorregan has breeding colonies of kittiwake Rissa tridactyla, razorbill Alca torda and guillemot Uria aalge. Cormorant Phalacrocorax carbo breed on Melledgan and storm petrel Hydrobates pelagicus breed in some of the granite boulder beaches throughout these western islands. The other breeding sea birds include puffin Fratercula arctica, fulmar Fulmarus glacialis, great black backed gull Larus marinus, lesser black backed gull L. fuscus and herring gull Larus argentatus. In addition the isolated rocks and islands of the Western Rocks provide the most important site on Scilly for grey seal Halichoerus grypus. Site Notified to the Secretary of State on 5 December 1986

Species mentioned

Insects to look out for

These moths, butterflies and beetles are known to feed on plants recorded at this site, and carry a notable UK conservation status — but a host-plant being present doesn't mean the insect has actually been recorded here. Treat this as "worth watching for," not a confirmed sighting.

Host-plant data: Cook et al. (2025), Traits data for the butterflies and macro-moths of Great Britain and Ireland, 2024, UK Centre for Ecology & Hydrology / Butterfly Conservation; and Padovani et al. (2020), Database of Insects and their Food Plants (DBIF), UK Centre for Ecology & Hydrology (both Open Government Licence). Contains data supplied by UK Centre for Ecology & Hydrology.