Evidence Against Observational Learning in Storage and Recovery of Seeds by Black-Capped Chickadees

-Recovery of cached sunflower seeds by Black-capped Chickadees (Parus atricapillus) was observed in four laboratory experiments. Results of the first experiment were consistent with the hypothesis that chickadees use spatial memory to recover seeds cached 24 h earlier. The second experiment demonstrated that individuals have a high recovery rate for their own caches and a low recovery rate for caches made by another. The third and fourth experiments demonstrated that one chickadee observing another caching seeds provided no recovery benefit to the observer in comparison to its performance when recovering seeds hidden in its absence. This result held for 2-h and for 6-min delays between observation and attempted recovery. We believe that spatial memory is used by chickadees, that the individual carrying out the caching has a large recovery advantage over a conspecific that searches the same patch, and that the perceptual and motor experience involved in the act of traveling to a cache location may be necessary for the establishment of spatial memory. Received 6 October 1987, accepted 14 March 1988. SEVERAL species of birds employ memory to recover food items cached previously (Tomback 1980, Cowie et al. 1981, Sherry et al. 1981, Kamil and Balda 1985). Research on cache recovery has documented both the existence of spatial memory and its accuracy in different species. Investigators have explored properties of memory such as decay, the role of local visual or odor cues in recovery, the sequence of recovery acts in relationship to storage acts, and the revisitation of cache sites from which the forager already recovered the food items (Bossema 1979, Shettleworth and Krebs 1982, Sherry et al. 1981, Vander Wall 1982, Sherry 1984a, Balda et al. 1986, Bunch and Tomback 1986). Less experimentation has been conducted on the social aspects of food storage and recovery of the cached items. Several food-caching birds, such as the Black-capped Chickadee (Parus atricapillus), cache and recover while members of a social flock. This context raises the possibility that other flock members may benefit to the detriment of the individual that cached the food (Andersson and Krebs 1978). Benefits could be gained if one bird searched randomly the local patch of environment used by the cacher and found the stored food; if the searcher had cachesite preferences identical to those of the cacher and found stored food by non-random searching; or, if a bird observed the cacher, remembered the cache locations, and subsequently recovered stored items. Cache loss appears to be high in some cases, e.g. Marsh Tits (Parus palustris) (Sherry et al. 1982), but little is known about causes of losses (Vander Wall and Smith 1987). Kinship within chickadee flocks is low, which suggests no important component of kin-correlated behavior in the caching/flock system throughout most of the flocking season. A few sibling or parent-offspring combinations are present in some flocks into the late summer (Weise and Meyer 1979). Food caching presumably is advantageous to individual chickadees caching food (Sherry 1985) even though the social context within which caching occurs might encourage substantial loss of caches to unrelated individuals. We developed three hypotheses to examine this assumption. The first hypothesis was that Black-capped Chickadees remember where they cache food items. Although this was established previously 492 The Auk 105: 492-497. July 1988 This content downloaded from 207.46. 13.53 on Thu, 01 Sep 2016 04:30:56 UTC All use subject to http://about.jstor. org/terms July 1988] Spatial Memory in Chickadees 493 (Sherry 1984a), it was important to confirm it in our experimental setting. The second hypothesis was that the cacher has a better recovery performance than another individual searching the same patch. It was necessary to test this experimentally because conspecifics may have highly convergent preferences for caching sites. If so, another individual would do as well as the cacher in recovering the caches. The third hypothesis concerned the possibility of one bird learning of the food caches made by another. We hypothesized that an observer watching a conspecific cache food cannot remember the locations of stored items. The development of a spatial memory may depend upon performing the motor activities of traveling to a caching location together with the perceptual processes attending that activity. Disproof of the third hypothesis would raise the possibility of "cheater" phenotypes (Andersson and Krebs 1978).