Male New Zealand robin (Petroica longipes) song repertoire size does not correlate with cognitive performance in the wild

Songbirds (Oscines) possess specialized brain regions responsible for the learning and production of their elaborate vocalizations. It has previously been suggested that song may provide a useful indicator of individual cognitive ability, due to its underlying neurobiology, individual variability, and links to developmental health. To date the relationship between song repertoire and cognitive performance has been most extensively examined in wild song sparrows (Melospiza melodia). Two initial studies found that song repertoire size was negatively correlated with spatial memory performance, but positively correlated with inhibitory control performance in a detour reaching task. However, a recent attempt to replicate this research found opposing patterns of association between each of these cognitive measures and song repertoire. It has been suggested that we may gain further insight into the relationship between song learning and other cognitive abilities by investigating species with different ecology to song sparrows, namely caching species. Here we re-examine the relationship between song repertoire size, spatial memory and detour reaching performance in a caching songbird, the toutouwai, or North Island robin (Petroica longipes). We tested both male and female toutouwai in a detour reaching task and a spatial memory task, while also recording the individual song repertoire size for 21 of the males tested. All experiments were carried out in the wild on individuals' territories. We found no associations between song repertoire and performance in either cognitive task, or between the two cognitive task performances. Our results provide further evidence that song repertoire is unlikely to be a useful signal of individual spatial memory and inhibitory control ability in songbirds.