Alderney’s Northern Gannet Morus bassanus population; Counts on Les Etacs and Ortac

Abstract

A population assessment of the Northern Gannet Morus bassanus on Alderney, Channel Islands, in June 2015 estimated a total of 8,737 Apparently Occupied Sites (AOS), split between the two gannetries with 5,960 AOS on Les Etacs and 2,777 AOS on Ortac. This was an annual increase of 2.3% and 0.9% for Les Etacs and Ortac respectively over the decade since the last count in 2005. However, both growth rates were below the average rate experienced by other UK Northern Gannet colonies during this same time period. Results show the reduced growth rates of the colonies may be due to them reaching carrying capacity with little room for further expansion.