Food storing and the hippocampus in corvids: amount and volume are correlated

Abstract

The volume of the hippocampal region (dorsomedial cortex) relative to body mass was measured in seven species of corvid (red-billed blue magpie, Cissa erythrorhyncha; European crow, Corvus corone; rook, C. frugilegus; jackdaw, C. monedula; jay, Garrulus glandarius; magpie, Pica pica; and Alpine chough, Pyrrhocorax graculus). The species studied differ in the extent to which they store food, and the results showed that there is a positive correlation between the estimated amount of food-storing behaviour and the relative volume of the hippocampus among the seven species. For two of the species, magpie and jackdaw, intraspecific variation was analysed. These two species show a sex difference in relative hippocampal volume (males larger than females), although there are no reports of sex differences in storing behaviour. In the magpie, which stores food regularly, hippocampal volume relative to body mass is positively related to relative volume of the rest of the telencephalon, whereas in the jackdaw, which rarely stores food, there is no relation.