Social Caching and Observational Spatial Memory in Pinyon Jays

Abstract

In the wild, pinyon jays (Gymnorhinus cyanocephalus) live in large, integrated flocks and cache tens of thousands of seeds per year. This study explored social aspects of caching and recovering by pinyon jays. In Experiment 1, birds cached in a large experimental room under three conditions: alone, paired with a dominant, and paired with a subordinate. In all cases, birds recovered caches alone seven days later. Individuals ate more seeds before caching when alone than when paired and started caching sooner when subordinate than when dominant. Pinyon jays accurately returned to sites containing their own caches but not to sites containing caches made by partner birds. However, they went to areas containing partner caches sooner than would be expected, indicating memory for the general areas containing caches made by other pinyon jays. In Experiments 2 and 3 birds were placed closer to each other and allowed to recover one or two days after caching. In Experiment 2, both free-flying and caged observers found caches with accuracies above chance. Cachers made significantly fewer errors than observers. During Experiment 3, caged observers saw the cachers recover some seeds one day after they were cached. On the next day cachers and observers were separately allowed to visit all cache sites. Both cachers and observers performed accurately and did not differ in accuracy. Neither group discriminated between extant and depleted caches. Observational spatial memory in pinyon jays may allow economical cache robbery by wild pinyon jays under some circumstances, particularly shortly after caches are created.