VIGILANCE IN BRONZE MANNIKIN GROUPS: THE CONTRIBUTIONS OF PREDATION RISK AND INTRA-GROUP COMPETITION

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Abstract
We describe foraging behaviour and time budgets of the gregarious bronze mannikin, Lonchura cucullata. In addition to being the first such study of a southern African granivore, this was the first study of a group-forager to differentiate between vigilance for other flock members (conspecifics) and vigilance for predators. We verified a perception of predation risk by placing five feeders at increasing distances from cover. The mean number of birds at a feeder decreased significantly with increasing distance from cover. We manipulated levels of aggression by restricting access to random numbers of feeding holes at various distances. The treatments succeeded in forcing birds to feed further from cover, and by inference, increased levels of aggression. We measured time budgets with focal samples on marked individuals. There was no influence of group size on time budgets. There was a non-significant (p < 0.06) trend for vigilance to increase with increasing distance from cover (predation risk). There was no pattern in the relative vigilance for predators as opposed to vigilance for other flock members (conspecifics), either with group size, distance from cover, or manipulated levels of aggression. Despite our inability to detect patterns of vigilance for other flock members, we emphasize the importance of studies to elucidate such a process.

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