Inhibition in Clark's nutcrackers (Nucifraga columbiana): results of a detour-reaching test.

Inhibition (i.e. the ability to restrain ineffective responses to a given stimulus) is a good indicator of complex cognitive abilities in animals. Inhibition has been demonstrated in a broad range of mammals with foraging style and social group size identified as potential influences of this ability. Whether these ecological factors also apply to birds has not been well studied. Corvids, a family of birds well known for being able to accomplish difficult cognitive tasks often requiring inhibition, are a good model for studying inhibitory control. During this study, we measured the ability of Clark's nutcrackers (Nucifraga columbiana), a relatively non-social, food specialist corvid to exercise inhibitory control during a detour-reaching test. Individuals had to retrieve a pine nut inserted into a transparent tube through one of the side openings without pecking directly at the nut from the front of the tube. Overall, nutcrackers were able to inhibit pecking directly at the food (i.e. prepotent response), instead detouring to the side to retrieve the reward. However, the nutcrackers first required a learning period before showing inhibitory control. The nutcrackers' ability to inhibit was lower than other corvids studied to date, and we discuss the implications of this result for the role of sociality and dietary breadth for the evolution of inhibitory control.