カラスのペリットの教材化に関する基礎的研究

抄録

An animal species’ diet constitutes the basic ecology of that species and is indispensable for understanding its ecological niche. Crows (Corvus corone and C. macrorhynchos) gather at communal roosts in winter and regurgitate indigestible portions of food as pellets on the ground under the roost. We used pellet analysis to determine crows’ diets and compared them between agricultural (Joetsu region, Niigata) and urban areas (Tokyo) in 2002 winter, The pellets were classified into plant animal and artificial matter. The major food substance in both areas was plant matter. The pellets collected in the Joetsu region were shaped like bullets and contained primarily seeds of Oryza sativa and Rhus spp. The pellets collected in Tokyo had loose texture and were flattened, and contained plant matter such as fruits and berries of trees and shrubs, Second in frequency to plant matter was artificia1 matter consisting of small pieces of white or transparent plastic usually used for garbage bags. Artificial matter also contained aluminum foil and paper, a1l of which are used for food wrappings, suggesting their association with food scraps. In this study, we discussed the utility of crow pellets for teaching food webs and the environmental issues such as garbage disposal.