Memory, Evolution, and the Brain of Food-storing Birds

摘要

Food-storing birds remember the spatial locations of thousands of scattered food caches for periods ranging from several days to many months. Food storing occurs seasonally, primarily in fall and winter, and birds rely on stored food to survive periods of scarcity. This prodigious memory for spatial locations raises a number of interesting problems in animal cognition that have been addressed in research with food-storing birds. Chickadees use at least two sources of information to identify cache sites, distal landmarks around cache sites, and bearing derived from a time-compensated sun compass. Lesions of the hippocampus disrupt memory for the locations of caches and also disrupt other tasks requiring spatial memory. Comparative research has shown that food-storing chickadees, jays, and nuthatches have a much larger hippocampus than closely-related non-storing birds. There is also seasonal variation in the size of the hippocampus that is correlated with the seasonal occurrence of food storing, and recent evidence shows a seasonal increase in neurogenesis in the chickadee hippocampus that coincides with the autumn onset of food storing. Food storing behaviour evolved independently in chickadees, jays, and nuthatches, indicating that modification of the hippocampus has also occurred independently in these birds in response to evolutionary pressures favouring the cognitive capacities required for remembering large numbers of spatial locations.