Clever Eurasian jays
First, the birds were given the choice of burying their food in sand or gravel. Gravel is, of course, the noisier alternative. Investigators noted which material each bird chose when alone, when the bird could see and hear that another bird was present, and when the bird could only hear that another bird was present. When the Eurasian jays knew that another bird was listening in, they chose to hide the food in the least noisy place. The birds probably made this choice to avoid drawing the attention of the bird that was spying, thus reduce the chance that their food would be stolen.
Next, the research focus shifted to the bird that was listening in, to see how much noise a jay made when watching another jay hiding food, another jay stealing the observing bird’s food, or another jay neither hiding nor stealing. When the jays were spying on another bird, they made much less noise than when alone. The researchers suspect that the jays are more quiet in order to keep another bird from noticing them and then hiding the food somewhere else.
The Eurasian jay is more clever than previously thought. Humans understand that other humans can hear what we are doing, but there is little evidence of this in the animal kingdom. The investigator asserts that this Eurasian jay study is the first to demonstrate that a member of the crow family takes eavesdroppers into account.