Nut-cracking behaviour, by means of automobiles, by Carrion Crows in Hakodate City

Abstract

The use of automobiles to crack open nuts by the Carrion Crow Corvus corone is a remarkable example of tool-use among birds. Previously only studied in Sendai City, during the 1990s, we studied this behavior in Hakodate City, Hokkaido, Japan during autumn and winter 2016, and compared our results with those from Sendai. Certain differences between them were noted. In Sendai, crows were observed to place walnuts in front of cars stationary at traffic signals. This efficient means of breaking walnuts was not observed during our study. Instead, in Hakodate, crows frequently dropped walnuts randomly from electric lines onto roads, which did not seem an effective way of placing the nuts where they were most likely to be broken. Our results suggest that the nut-cracking behavior of Carrion Crows in Hakodate is less sophisticated than that in Sendai. The difference may be a consequnce of several factors such as the length of the cultural learning period history, the learning environment, or features of the walnuts.