An aerial survey of gannets on Westray, Orkney, in August 2016

An aerial survey of the Gannet colony on Westray, Orkney, was made for the first time on 16 August 2016 and found 1,560 AOS, contrasting with a land survey made on 30 May 2016, which found 1,020 AON. The aerial survey photographs show areas of the cliffs that are hidden from land. This, and the different count units used, are the main reasons for the higher aerial survey figure. A third population estimate was made by combining breeding productivity figures from an RSPB monitoring plot with chicks visible in the aerial photographs, which gave a calculated estimate of 1,306 AON. Whichever population estimate is used, it is clear that the colony is expanding rapidly. Future land counts will likely underestimate numbers so would best be combined with an occasional aerial survey to more precisely define colony size.