Western Scrub Jays (like this beauty) and their corvid relatives (crows, magpies, rooks) are birds that collect and cache food, to be eaten at a later date.
Robb and I have been enjoying watching our local jays bustle around with acorns in their bills. They bury the acorns, look around, cock their heads to one side, dig the acorns up, and re-bury them. I particularly enjoy watching the jays "disguise" their food caches, by scattering dry leaves on top of their buried treasure.
I recently ran across a series of articles about this behavior.
Food-caching corvids hide food, but such caches are susceptible to pilfering by other individuals. Consequently, the birds use several counter strategies to protect their caches from theft, e.g. hiding most of them out of sight. When observed by potential pilferers at the time of caching, experienced jays that have been thieves themselves, take further protective action. Once the potential pilferers have left, they move caches those birds have seen, re-hiding them in new places. Naive birds that had no thieving experience do not do so. By focusing on the counter strategies of the cacher when previously observed by a potential pilferer, these results raise the intriguing possibility that re-caching is based on a form of mental attribution, namely the simulation of another bird's viewpoint. Furthermore, the jays also keep track of the observer which was watching when they cached and take protective action accordingly, thus suggesting that they may also be aware of others' knowledge states.
What's so interesting here is that not only have the jays learned to steal from other jays, they are able to anticipate theft of their own hidden food. These animals seem to have the cognitive ability to keep track of which jays have figured out the idea of theft, and which ones have not. They seem to vary their behavior based on their understanding of how much their fellow-jays know about robbing food caches.
Robb and I were talking about this, and he reminded me that the ability to imagine another individual's thought process takes years to develop in humans.
Those cache-ers are a devious bunch!