Invasive alien plants are not the only threat to the wildlife of Ascension. Human settlers also brought with them rats and cats, which have had devastating effects upon the breeding population of seabirds such as the endemic Ascension frigatebird Fregata aquila. While breeding populations of seabirds were once estimated at 20 million breeding pairs on the main island, these were reduced to only a few small nesting colonies most of which took refuge on offshore stacks. |