Abstract
Magnetic compass orientation in a night-migratory songbird requires that Cluster N, a cluster of forebrain regions, is functional.
Cluster N, which receives input from the eyes via the thalamofugal pathway, shows high neuronal activity in night-migrants
performing magnetic compass-guided behaviour at night, whereas no activation is observed during the day, and covering up the
birds’ eyes strongly reduces neuronal activation. These findings suggest that Cluster N processes light-dependent magnetic
compass information in night-migrating songbirds. The aim of this study was to test if Cluster N is active during daytime migration. We
used behavioural molecular mapping based on ZENK activation to investigate if Cluster N is active in the meadow pipit (Anthus
pratensis), a day- and night-migratory species. We found that Cluster N of meadow pipits shows high neuronal activity under dim-light
at night, but not under full room-light conditions during the day. These data suggest that, in day- and night-migratory meadow pipits,
the light-dependent magnetic compass, which requires an active Cluster N, may only be used during night-time, whereas another
magnetosensory mechanism and ⁄ or other reference system(s), like the sun or polarized light, may be used as primary orientation
cues during the day.