Turkey vultures were observed foraging alone and in groups of up to 16 individuals. Vigilance behavior was quantified by monitoring 4 aspects of vulture foraging behavior (proportion ofhead up time, number of head raises per minute, time interval between head raises, and proportion of time spent foraging during foraging bouts). Although solitary foragers spent 91% of their foraging bouts actively foraging, a greater proportion (47%)of their foraging time was spent with their heads up compared to individuals occurring in groups (<29%). Similarly, individuals in small groups (2-3 and 5-7) were more vigilant than individuals in large groups (8-16). Solitary foraging vultures raised their heads at a significantly higher rate than those foraging in groups of 5-7 or 8-16 and had significantly shorter intervals between head raises than group foragers. Large group foragers were able to minimize their vulnerability to predation because at least one head was up during the entire foraging bout. Results of this study were consistent with the 'many-eyes, hypothesis that individuals in a foraging group can feed at a faster rate by reducing vigilance time as the number of individuals scanning for predators increases (Pulliam, H. R. 1973. J. Theor. Biol. 38: 419-422).Key Words: turkey vulture, vulture, vigilance, foraging behavior, group size, Indiana. / Department of Biology

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