Conflict between Humans and Crows in Greater Tokyo — Garbage Management as a Possible Solution —

Abstract

　Complaints by the citizens against crows increased during the 1990s in Tokyo, mostly because crows’ scavenging caused a mess at communal garbage collection stations. We conducted a few pilot studies on counter-scavenging measures and assessed those of local governments so as to find possible solutions to conflicts between man and crows in urbanized areas. Assessment of social aspects was done by questionnaires to the citizens, and field surveys on the actual state of crows and garbage.

　The citizens’ complaints had biases. Their value, therefore, was limited as an indication of the existence of conflicts. The field surveys revealed that crows occurred at higher densities in central Tokyo than in the suburbs, contrary to conventional concepts. Compiling the results of the complaints and analyzing the field surveys were two indispensable procedures to seek for possible solutions.

　The assessments of the pilot projects showed three realistic approaches to countering the scavenging of garbage. Reducing the amount of food scraps was the only solution that would work against all types of scavengers. The second option was the temporal segregation of food scraps from diurnal scavengers (midnight/early morning garbage collection and time-specific collection). Spatial segregation of garbage from scavengers by protective nets and containers had variable effects.

　The responses to the questionnaires showed that where scavenging by crows decreased, so did people’s negative feelings towards crows. Therefore, we suggest that counter-scavenging measures could solve a major part of the crow-man conflict in urbanized areas.