The author made an investigation on the seasonal change of impalements by shrikes during a period from Sept. 1975 through March 1976 in Mizumoto Park, the northeastern part of Tokyo. The results obtained are as follows.
1) The total number of impalements observed was 129 individual animals. Of these, 120 impalements (92%) were made between November and February.
2) Insects (especially Locustidae and Gryllidae) and frogs (Rana catesbiana) were the main victims in October and November. From December to February, aquatic animals (e.g., fishes and crustaceans), and soil animals (earthworms, etc.) became the main preys.
3) Approximately 93.7% of the impalements disappeared within two months after the impalements were made, but after three months some of the remaining impalements become too hard to be edible.
4) Seasonal changes in the number of shrikes and that of their impalements is shown in Fig. 2. During September and October, the number of shrikes increased to 22, but the number of impalements decreased to only three. During the winter season from November through February only four shrikes was observed in their territories, but the number of impalements increased rapidly.
5) Four winter territories of shrikes were formed in Mizumoto Park and each shrike occupied favorite places for impaling, such as thorny iron wires or branches of trees, within each territory.
6) The possibility of eating impalements by shrikes within their territories in winter is briefly discussed.