Meeting Abstract

P2.20  Jan. 5  Age affects relative but not absolute hippocampal volume in migratory Mountain White-Crowned Sparrows SANFORD, K.H.*; BREUNER, C.W.; HAHN, T.P.; PRAVOSUDOV, V.V.; Univ. of California, Davis; Univ. of Texas, Austin; Univ. of California, Davis; Univ. of Nevada, Reno khsanford@ucdavis.edu

The hippocampus (HF) is necessary for the formation of spatial memories. Migratory birds rely in part on spatial memory for navigation, and research suggests HF is important in migration. However, few studies have investigated HF development in migratory birds. We hypothesized that HF in migrants is experience-dependant, and that migration affects development of the avian HF. Mountain White-Crowned Sparrows (Zonotrichia leucophrys oriantha; MWCS), intermediate-distance migrants, breed in sub-alpine meadows of the northwestern US and winter in the southwest and northern Mexico. Brains from 14 wild MWCS (2 juvenile males, 6 juvenile females, 3 adult males, and 3 adult females) from California’s high-Sierra mountains were used to asses the development of HF. All birds were caught in late summer prior to migration to insure that the juveniles were developmentally independent, but had not yet experienced migration. Adults were assumed to have had at least one year of migratory experience. HF and telencephalon (T) volumes for each bird were calculated, and HF neurons were counted. Juveniles had significantly larger volume T than adults, and HF volume relative to T was larger in adults than in juveniles. There was no difference in number of HF neurons relative to T. Neither absolute HF volume or neuron count changed with age. However, the absolute volume of the left side of the HF was smaller than the right in juveniles. For all birds, the left side of the hippocampus had absolutely more neurons than the right. These results suggest varying resource allocation between T and HF, and support a stimulatory role for experience in HF development although age and experience were not separated.