Neuronal activation in the geomagnetic responsive region Cluster N covaries with nocturnal migratory restlessness in white‐throated sparrows (Zonotrichia albicollis)

Abstract

AbstractCluster N is a region of the visual forebrain of nocturnally migrating songbirds that supports the geomagnetic compass of nocturnal migrants. Cluster N expresses immediate‐early genes (ZENK), indicating neuronal activation. This neuronal activity has only been recorded at night during the migratory season. Night‐to‐night variation in Cluster N activity in relation to migratory behaviour has not been previously examined. We tested whether Cluster N is activated only when birds are motivated to migrate and presumably engage their magnetic compass. We measured immediate‐early gene activation in Cluster N of white‐throated sparrows (Zonotrichia albicollis) in three conditions: daytime, nighttime migratory restless and nighttime resting. Birds in the nighttime migratory restlessness group had significantly greater numbers of ZENK‐labelled cells in Cluster N compared to both the daytime and the nighttime resting groups. Additionally, the degree of migratory restlessness was positively correlated with the number of ZENK‐labelled cells in the nighttime migratory restless group. Our study adds to the number of species observed to have neural activation in Cluster N and demonstrates for the first time that immediate early gene activation in Cluster N is correlated with the amount of active migratory behaviour displayed across sampled individuals. We conclude that Cluster N is facultatively regulated by the motivation to migrate, together with nocturnal activity, rather than obligatorily active during the migration season.