Shady deals

It is widely observed that many members of the crow family can appear quite clever to humans. Several species have learnt to store food for future use when in excess. But the problem is that other individuals are smart enough to spot where an individual has hidden food and then go and take it. Therefore many species have developed strategies to lessen the chances that their food store will be robbed. Field observations suggest that storers implement a variety of measures to reduce cache theft. These strategies include waiting until other individuals have left or are distracted before hiding food, or returning alone to stores previously hidden in the presence of other individuals and removing the food to another site. New insights into the foodstoring behaviour of one such crow species, the scrub jay, have come from lab experiments on individual scrub jays, reported by Joanna Dally, Nathan Emery and Nicola Clayton at the University of Cambridge in a paper published in The Proceedings of the Royal Society Biology Letters (published online). The aim of the experiment was was to test whether jays might also use shade as a means of protecting their stored food. If jays act to reduce the visual information available to another bird at the time of storing food, they should prefer shady sites over ones in full light, but they should not make such a preference if unobserved, the researchers believed. To test the hypothesis, the captive jays were allowed to to store food in private and also when observed by another bird. In each condition they were provided with two trays that were equidistant from the observing bird’s cage. For the experiment, one tray was paced in full light and the other one was in the shade. The researchers found that the jay’s behaviour changed significantly when they were being observed by another bird in an adjacent cage. When observed, the jays preferentially stored food in the shaded tray, whereas both trays were used equally when they were storing food in private. By storing in shaded sites, the quality of and transfer of visual information available to the observing bird is reduced, thereby making the location of the stored food less certain. The results suggest that scrub jays may selectively store food at shaded sites as a strategy to reduce the chance of theft of the food by other birds in the vicinity. The results raise several questions about crow intelligence and add to information on other strategies such as storing out of view, moving stored food and seeking sites away from other observing birds. Shady deals