The isles provide nesting for a population of seabirds, including Atlantic puffins, northern fulmars, European storm-petrels, Leach's petrels, common shag, and black-legged kittiwakes. There is a gannetry on Roaireim. From the late Middle Ages on, Lewismen regularly raided these nests for eggs, birds, and feathers. There is a population of rabbits, brought to the islands by the lighthouse keepers, and crofters from Bernera graze sheep on the most fertile islands. Minke and pilot whales, as well as Risso's and other species of dolphin are commonly observed in the vicinity.