Birds as a Geological Agent

Abstract

ALL along the tops of the cliffs of the Undercliff from Ventnor to Blackgang empty shells of the common limpet are found in large numbers, and it has usually been assumed that their shape has caused them to be blown by the wind from the beach over the cliffs. There are so many of them that I have found it difficult to believe this theory, and on mentioning it to a local naturalist, he has assured me that he has seen rooks and jackdaws pick them up from off the rocks while living, and convey them in their beaks to the trees where they roost and nest and to other places, and after feeding on them, cast away the empty shells. This may account for the mixture of marine shells with land shells in some of the tertiary strata which is sometimes inexplicable.