Cache Pilfering and Its Prevention in Pairs of Black-Capped Chickadees

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Black-capped Chickadees Parus atricapillus scatter hoard food. Because they live in social groups during the winter, flock members may observe caching by others and take their caches. We present two laboratory experiments that investigate the possibility of observational learning of cache location and related behaviours. In the first experiment, 15 chickadees were observed storing food in an indoor aviary, either individually or in pairs. Five percent of caches were taken within a few minutes by birds that observed the occurrence of caching. These cache thefts may have been assisted by observation. Dominant birds made more caches and subordinate birds were more likely to take another bird's caches. When cache recovery was tested several hours later, birds recovered their own caches more accurately than those of other birds but recovery of other birds' caches was not improved by the previous observation of caching. A second experiment with 6 additional chickadees examined whether birds attempt to conceal their caching activity. In this experiment 9% of caches were taken by birds that had the opportunity to observe caching. When birds carried seeds, they flew away from their companion more than they did when they were flying without a seed. Overall, these results are consistent with those of previous laboratory studies and suggest that conspecific cache theft may be relatively rare in flocks of food-storing chickadees.