century clearance. There was major rebuilding of the broch from 1967 until the 1980s. In January 2005 it was announced that archaeologists had used 3D laser scanning to investigate the structure in detail for further possible repairs. Storm petrels Mousa Broch is well known among birders for its breeding European storm petrels, which are best seen after dark on partly or on completely overcast summer nights. The island holds around 6,800 breeding pairs in total, representing about 8% of the British population and about 2.6% of the world population. Some of these birds nest in burrows within the broch itself. See also Oldest buildings in Scotland References Further reading Armit, I. (2003) Towers in the North: The Brochs of Scotland. Stroud. Tempus. E W MacKie 2002 The roundhouses, brochs and wheelhouses of Atlantic Scotland c. 700 BC - 500: architecture and material culture. Part 1: the Orkney and Shetland Isles. BAR British series 342: Oxford. Section 2 and site HU46 6, pp. 82–87 & illustrations. RCAHMS 1946, vol. 3, no. 1206, pp. 48–55 & illustrations. (Royal Commission on the Ancient and Historical Monuments of Scotland) Edinburgh. External links D. Thomas 2011 'An Investigation of Aural Space inside Mousa Broch by Observation and Analysis of Sound and Light', Internet Archaeology 30. Mousa Broch at Historic Scotland. Mousa Broch, Shetland structure at Sketchfab by Historic Environment Scotland Mousa Historic Scotland properties in Shetland Scheduled Ancient Monuments in Shetland Buildings and structures completed in the 1st century BC