Food storing and the hippocampus in Paridae.

Food storing passerines have a larger hippocampus, relative to the rest of the telencephalon and/or body mass, than do non-storing species. This study looked at the relationship between relative size of the hippocampus and degree of food storing in six species of Paridae (blue tit, Parus caeruleus, great tit, P major, marsh tit, P palustris, coal tit, P ater, black-capped chickadee, P. atricapillus, and willow tit, P montanus). The degree of storing by these species varies from little or none to thousands of food items. The period over which food is stored also varies from a few hours to several months. The results showed that hippocampal volume, relative to the rest of the telencephalon, is larger in those species that store more food, store for longer, or both. In an analysis of intraspecific variation within two of the species, the food storing marsh tit and the non-storing blue tit, there was a significant positive relationship between hippocampal volume relative to body mass, and telencephalic volume relative to body mass, in the marsh tit but no relationship between these variables in the blue tit.