Data from: Diel rhythmicity of activity and corticosterone metabolites in Arctic barnacle geese during breeding

Birds that migrate from temperate areas to the Arctic to breed lose their
strongest Zeitgeber of circadian organization when they cross the Arctic
Circle in spring – the 24h light-dark cycle. Under continuous daylight,
diverse behavioral and physiological patterns have been detected in both
free-ranging and laboratory animals. To better understand the evolution of
plasticity in circadian clocks, it is essential to study behavioral and
physiological rhythmicity in the context of a species' ecology.
Employing a multifaceted approach, which included wildlife cameras,
accelerometers, and non-invasive sampling of hormone metabolites, we
investigated activity patterns and corticosterone rhythmicity in a
migratory herbivore, the barnacle goose (Branta leucopsis), during its
Arctic breeding season on Svalbard. We found that females showed a
combination of both ultradian and diel rhythmicity in nest recesses and
sleep during incubation. In both parents, these rhythms in activity
continued also during the gosling rearing phase. During molt, many geese
aligned activity with the prevailing tidal rhythm. Barnacle geese showed
weak diel rhythmicity in excreted corticosterone metabolites (CORTm). This
suggests that while Arctic geese may adopt an alternative Zeitgeber during
the Arctic summer to maintain a diel rhythm, ultradian rhythmicity remains
essential, allowing the geese to flexibly adjust their rhythms to
environmental conditions.