It takes one to know one, in this Moment of Science.
In several laboratory experiments scrub jays, relatives of the blue jay, hid their extra food more cautiously when other jays were around. In fact, if another scrub jay was visible when the first jay buried its food, the first jay was more likely to dig up the food later and rebury it in another location.
This shows that some birds are capable of more complicated behavior than we previously thought. Scrub jays are notorious for stealing food from each other; the fact that they behave more cautiously when other scrub jays are present might mean that they're able to speculate about the future behavior of their observers. Birds from species not known for thievery don't show the same reburying behavior. When scientists allowed some scrub jays to dig up another jay's food after seeing where it was buried, the birds allowed to steal were more likely to rebury their own food later, when given the chance.