Septum Volume and Food-Storing Behavior Are Related in Parids Michael W. Shiflett, 1 Kristy L. Gould, 1 Tom V. Smulders, 2 Timothy J. DeVoogd 1 1 Department of Psychology, Cornell University, Uris Hall, Ithaca, New York 14853 2 Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710 Received 20 September 2001; accepted 8 January 2002 ABSTRACT: The hippocampal formation (HF) of food-storing birds is larger than non-storing species, and the size of the HF in food-storing Black-Capped Chick- adees (Poecile atricapillus) varies seasonally. We exam- ined whether the volume of the septum, a medial fore- brain structure that shares reciprocal connections with the HF, demonstrates the same species and seasonal variation as has been shown in the HF. We compared septum volume in three parid species; non-storing Blue Tits (Parus caeruleus) and Great Tits (Parus major), and food-storing Black-Capped Chickadees. We found the relative septum volume to be larger in chickadees than in the non-storing species. We also compared septum and nucleus of the diagonal band (NDB) volume of Black-Capped Chickadees at differ- ent times of the year. We found that the relative septum volume varies seasonally in food-storing birds. The volume of the NDB does not vary seasonally. Due to the observed species and seasonal variation, the septum, like the hippocampal formation of food-stor- ing birds, may be specialized for some aspects of food-storing and spatial memory. © 2002 Wiley Periodi- cals, Inc. J Neurobiol 51: 215–222, 2002 Keywords: food storing; septum; hippocampus; chicka- dee; paridae INTRODUCTION Behaviors that rely on an accurate and extensive memory for spatial locations, such as homing in pi- geons and food caching in some avian species, re- quires a functioning hippocampal formation (HF) (Sherry and Vaccarino, 1989; Bingman et al., 1995; Hampton and Shettleworth, 1996; Gagliardo et al., 1999; Strasser and Bingman, 1999). Furthermore, the HF is larger with respect to telencephalon in such species than in species that do not show these behav- iors (Krebs et al., 1989; Healy and Krebs, 1992; Hampton et al., 1995; Rehkamper et al., 1995). In at least one food-storing species, the Black-Capped Chickadee (Poecile atricapillus), an increase in cach- ing behavior in the Fall coincides with an increase in the volume and number of neurons in the HF (Smul- ders et al., 1995, 2000b), which is likely due to an increase in the survival of newly generated neurons in the HF (Barnea and Nottebohm, 1994, 1996). The avian HF shares reciprocal connections with the septum, a set of forebrain nuclei consisting of the medial and lateral septum and the nucleus of the diagonal band (NDB) (Krayniak and Siegel, 1978a,b; Szekely and Krebs, 1996; Szekely, 1999). In birds, the septum is known to be involved in the regulation of aggression and courtship behavior (Cooper and Erick- son, 1976; Goodson et al., 1999). This function is likely a result of the septum’s connections with hy- pothalamic nuclei (Krayniak and Siegel, 1978b). The function of reciprocal connections between the hip- Correspondence to: M.W. Shiflett (mws14@cornell.edu). Contract grant sponsor: National Institutes of Health; contract grant number: MH56093 (T.J.D.). Contract grant sponsor: National Institutes of Health; contract grant number: MH12934 (M.W.S.). © 2002 Wiley Periodicals, Inc. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/neu.10054 215