Bibliographic entry:

Dally JM, Emery NJ, Clayton NS (2006) “Food-caching western scrub-jays keep track of who was watching when.” Science 312(5780):1662-5

Abstract:

Western scrub-jays (Aphelocoma californica) hide food caches for future consumption, steal others' caches, and engage in tactics to minimize the chance that their own caches will be stolen. We show that scrub-jays remember which individual watched them during particular caching events and alter their recaching behavior accordingly. We found no evidence to suggest that a storer's use of cache protection tactics is cued by the observer's behavior.