The island differentiated itself from many of the others in the Aleutian chain by supporting a large diverse group of seabirds, most famously for their colony of more than 100,000 crested auklets and 150,000 least auklets, which was one of only seven colonies in the Aleutian chain. Other species included seabirds such as the Fork-tailed petrel, the whiskered auklet, the ancient murrelet, gulls, guillemots, and cormorants. These seabirds attracted many avian predators as well, such as bald eagles and peregrine falcons. The birds of Kasatochi were the dominant vertebrates on the island and the most prominent link between the terrestrial and marine ecosystems.