Clark's Nutcracker (Aves: Corvidae) Spatial Memory: Interference Effects on Cache Recovery Performance?

Clark's nutcrackers, Nucifraga columbiana , accurately v recover thousands of caches per year in the field. Previous experiments have confirmed that these birds possess excellent, long‐lasting spatial‐memory capabilities. We tested whether resistance to interference is one of the features of nutcracker spatial memory. Experiment 1 tested retroactive interference. Nutcrackers showed no decrease in accuracy overall but performed relatively poorly in their final recovery session. Interference is unlikely to have caused these sites to be poorly remembered because they had fewer neighbouring cache sites than better‐remembered sites. Experiment 2 tested for proactive interference. Interference would have caused the experimental birds to be less accurate than control birds. Instead then were slightly more accurate. In experiment 3, nutcrackers were allowed to repeatedly view their cache sites from a cage between caching and recovery. Nutcrackers were less accurate when recovering from cache sites they had viewed. This effect may be due to changes in motivation. Order of caching had no effect on accuracy but nutcrackers were more accurate when recovering caches from central than from peripheral areas of experimental rooms. In summary, these experiments provide further evidence of the remarkable spatial‐memory abilities of Clark's nutcrackers and demonstrate that these birds are highly resistant to interference effects on spatial memory. Comparative tests will be needed to test if specialized food storers are exceptionally resistant to interference in spatial memory.