Crows Do Not Use Automobiles as Nutcrackers: Putting an Anecdote to the Test

hook-tools (Hunt 1996). In many cases only a single instance of the putative intelligent behavior has been observed (e.g. Montevecchi 1978, Andersson 1989). One behavior, the use of automobiles to crack open nuts, has been cited repeatedly as an example of corvid resourcefulness and adaptability (e.g. Beck 1980:127, Hunt 1996). There are only two original reports of this behavior in the literature, both based on single observations of Western American Crows (Corvus brachyrhynchos hesperis) that dropped hard-shelled fruits onto paved roads and ate them after they were crushed by passing cars (Maple 1974, Grobecker and Pietsch 1978). Many species of birds, including at least six corvids, regularly drop food items onto hard surfaces to expose dible parts (Zach 1979). Consequently, the apparent behavior of crows using cars to crack nuts may be an incidental byproduct of using paved surfaces to open hard-shelled food. We conducted observations of crows feeding on walnuts (Juglans regia and J. hindsii) to determine whether crows behave in such a way as to facilitate the crushing of nuts by cars. Observations occurred at two locations in Davis, California, the site of Maple's (1974) original report of crows using cars as "nutcrackers." During autumn and winter in Davis, crows frequently attempt to open walnuts on paved surfaces by dropping them from a height or striking partly cracked nuts with their bills while holding them with their feet. One site where this occurred was Birch Lane, which had moderate traffic (mean of 39.8 vehicles/lane/h during observation periods) and approximately 50 large walnut trees along a two-block stretch. Observations were made here for