Cognitive ability and the evolution of multiple behavioral display traits

Males of many species have multiple behavioral display traits. Females may be able to use these multiple behavioral display traits together to evaluate a male’s overall cognitive ability, which may be related to his genetic quality. It is also possible that individual behavioral display traits indicate unique aspects of male quality possibly related to cognitive performance. We tested predictions of these 2 hypotheses in satin bowerbirds, Ptilonorhynchus violaceus, a species with a large number of behavioral display traits involved in mate choice. We calculated 2 integrative measures of male performance on 6 cognitive tasks. An aggregate measure of male display quality (produced from 4 behavioral display traits) was correlated with one of these measures of overall cognitive ability and with mating success. Multiple behavioral display traits used together, rather than individually, more accurately predicted this measure of overall cognitive ability. In addition, we found some support for the hypothesis that separate display traits may indicate different aspects of male quality. One display trait indicated male age and possibly survivability. These results suggest that multiple behavioral display traits may have evolved in part because of the large variety of information they can convey about male quality.