Ailsa Craig is also known as "Paddy's Mile Stone" as it lies halfway between the cities of Glasgow and Belfast. As well as being a local landmark and a well known marine navigational hazard the island is a protected bird sanctuary, sheltering thousands of breeding pairs of sea birds.
Ailsa Craig is also referred to as "Paddy's Mile Stone" due to its location equidistant from Glasgow and Belfast, in addition to serving as a notable local landmark and marine navigational hazard, while also providing a protected habitat for numerous breeding pairs of sea birds.