A study of breeding pairs of kittiwakes (Rissa tridactyla\textit{Rissa tridactyla}Rissa tridactyla) on an island colony was conducted over several decades. In 1986, the number of breeding pairs recorded was 11,800. In 2018, the number of breeding pairs recorded was 2,350.
Calculate the mean annual decrease in the population of individual kittiwakes in this colony between 1986 and 2018. Assume each breeding pair consists of two individual birds. Show your working. Give your answer to three significant figures and include the units.
