 Ten nests being occupied in a single small bay of only 7.5 mi (12 km) of coastline, and a total of 21 nests on the whole island.Unfortunately this astounding concentration of peregrine falcons was intimately linked to the very robust local seabird population that has declined since the 1950s due to unknown factors.Possible culprits for the decline include introduced non-native predators of seabirds such as rats and raccoons, coupled with possible changes brought on by human activities in the oceanic food chain on which the seabird colonies depend.