Analysis of owl pellets has been used for predator food studies (e.g. Cunningham 1960), determining species distributions (e.g. Twente and Baker 1951), interpreting paleontological finds (e.g. Brain and Brain 1977), and for estimating mammalian populations (e.g. Cabon-Raczynska and Ruprecht 1977). The senior author has used owl pellets in environmental impact studies, reducing the cost of the rodent species list and the impact of the assessment itself on the living fauna of the area. Owls may preferentially select prey species (Voight and Glenn-Lewin 1978); thus, pellet analysis is useful for verifying what species are in an area, not as proof of their absence. Owl pellet analysis is also a simple but rewarding laboratory exercise in ecology classes.