Hill of Colvadale and Sobul

Also within

Shetland County

Condition (NatureScot)

Geology & landscape

Rock Type: Serpentinite

Birds & fish recorded

Birds

Description

HILL OF COLVADALE AND SOBUL Hill of Colvadale and Sobul Site of Special Scientific Interest (SSSI) is located on the island of Unst in Shetland, to the east of the A968 between Uyeasound and Baltasound. It covers the hill of Sobul in the south, Helliers Water, the east side of the Hill of Calback and the north-western slopes of the Hill of Colvadale and Virda Field. The site is notified for its species-rich serpentine heath and debris vegetation which includes the rare Arctic sandwort Arenaria norvegica ssp. norvegica. It also supports a wide variety of breeding birds, in particular Arctic skua and whimbrel. The Hill of Colvadale and Sobul SSSI provides one of the best examples in Shetland of nationally rare serpentine heath habitat. It is part of an extensive area of rock-strewn bedrock, rock debris and heathland overlying the main north-south trending belts of serpentinite and ‘greenstone’ metagabbro of eastern Unst. The area contains a range of serpentine vegetation types ranging from herb-rich sedge-grass heath with woolly fringe-moss Racomitrium lanuginosum hummocks towards the south of the site, to relatively herb-poor heath with cross-leaved heath Erica tetralix in the Caldback and Hill of Colvadale area. This northern section is dominated by wet-flushed screes. The site provides habitat for an outstanding assemblage of breeding upland birds. Nine different wader species are present. Most of these are concentrated on the serpentine heaths where dunlin, curlew and golden plover breed. Most important at national level are the large aggregations of whimbrel (about 2.8% of the British breeding population) and Arctic skua (about 1.6% of the British breeding population). Patches of dry serpentine debris on Sobul support the nationally rare Arctic sandwort. In Shetland, the species is restricted to a small number of sites in Unst.

Species mentioned