Differences between the remains of mammalian prey in pellets of diurnal and nocturnal avian predators are discussed on the basis of recent material and in relation to probable fossil occurrences. The ability of diurnal predators to digest bone reduces the value of their pellets for quantitative or qualitative indications of the regional mammalian fauna. However, the remaining partially digested fragments in pellets of diurnal predators appear to have a characteristic morphology which may be recognised in a sample of fossil mammalian teeth from the type Cromerian Upper Freshwater Bed sediments at West Runton, England. The implications of such an origin for faunal analysis are briefly considered.

This is believed to be the first time that the role of diurnal predatory birds in accumulation of fossil vertebrate material has been recognised. The characteristically digested teeth from diurnal predator pellets may provide the only direct indication of the origin of at least a part of the mammalian material contained in deposits formed in open sedimentary environments where skeletal parts have been dissociated.