Many seed-eating birds, especially among the Corvidae (the crows and jays) and Paridae (tits and chickadees), store their food in caches to use at a later time. These birds must use spatial memory to re-locate their stored food items. Clark’s nutcrackers (Nucifraga columbiana) are a particularly extreme case. Each bird creates thousands of cache sites in the fall and remembers the locations for many months. These features of their ecology and natural history have made nutcrackers a focus of research on spatial cognition for over 25 years.

One of the central themes of our research has been testing the hypothesis that species that cache large numbers of seeds have been selected to have a better spatial memory. In a series of experiments comparing Clark’s nutcrackers to other New World, seed-caching corvids, we applied the "convergent operation" approach (Kamil 1988), testing for species differences in spatial memory along a number of different dimensions. We found that nutcrackers and pinyon jays recovered caches better than western scrub jays (Balda & Kamil 1989), and performed better than either scrub jays or Mexican jays in an open-room analog of the radial-arm maze (Kamil, Balda & Olson 1994). Olson (1991) found that nutcrackers also performed better than western scrub jays or pigeons on a spatial memory task in which the birds were required to remember a location defined by a pecking key on the wall of an operant chamber.

A crucial pair of experiments were carried out by Olson, Kamil, Balda & Nims (1995). In the first, the birds were simply required to remember the spatial position of a stimulus. We found that nutcrackers performed better than pinyon jays, scrub jays or Mexican jays on this task. In the second experiment, the same birds were tested on an identical nonspatial task, being required to remember the color of a stimulus rather than its location. This change in the nature of the information they had to remember completely changed the pattern of results. None of the species differences in the color memory task were statistically significant, but the pinyon jays performed best. These results are in strong agreement with the hypothesis that selection in seed-caching birds has favored spatial memory, rather than some more general memory ability.

"Let's see, now. Where did I leave that?"