SOCIAL-DOMINANCE IN MIGRANT AND RESIDENT TURKEY VULTURES AT CARCASSES- EVIDENCE FOR A DESPOTIC DISTRIBUTION

We placed carcasses in three different vegetation types in the heterog eneous savannas of central Venezuela to investigate the role of social dominance in habitat use by flocking migrant and resident turkey vult ures (Cathartes aura meridionalis and C. a. ruficollis). Migrants fora ged primarily in savanna habitats while residents foraged almost exclu sively in gallery forest. In the gallery forest residents discovered c arrion first significantly more often than migrants, despite there bei ng equal densities of residents and migrants foraging over this habita t. Because residents fed in smaller groups than migrants at carcasses they had higher feeding rates. There was also a negative relationship between group sizes of residents and migrants. The feeding rate of res idents declined in response to increased group size of migrants, but g roup size of residents had no effect. Migrant group size also had a gr eater effect on resident feeding rates than king vulture presence or a bsence. When the effect of migrant and resident group size on feeding rates in migrants was compared, the most significant factor was migran t group size. A second analysis showed that both resident group size a nd presence or absence of king vultures had a significant effect on fe eding rates in migrants. Rates of agonistic encounters in migrant and resident turkey vultures increased weakly in relation to group size. H owever, there was an increase in residents' encounter rate with migran ts in relation to increased migrant group size; there was no differenc e in resident encounter rates with other residents in relation to resi dent group size. Migrants dominated residents in almost all agonistic interactions over carcasses. We suggest that savanna habitats were les s attractive to residents for foraging because they held larger groups of migrants.