Abstract
Conspicuousness increases the risk of predation. One strategy to reduce this risk is to increase vigilance. We investigated the frequency of head movements as a measure of vigilance at waterholes in two related songbird species that differed in their conspicuousness: the Gouldian finch and the long-tailed finch. While both species showed a high frequency of head movements (high vigilance) when sitting in an open tree, the more colourful Gouldian finch remained more vigilant than the less conspicuous long-tailed finch when sitting under cover. Moreover, juvenile Gouldian finches had similar vigilance levels than adults; whereas, juveniles of the long-tailed finch were less vigilant, possibly because of staying in the family group. Furthermore, both species showed a similar temporal course of vigilance with a fast decrease in vigilance after landing in the tree, which was affected by group size. Single individuals had much higher vigilance than groups of birds. Finally, vigilance was higher at small waterholes. The results show that conspicuousness, uncertainty when arriving at waterholes, and higher perceived risk at small waterholes increased vigilance.