Circadian control of nocturnal songbird migration

Timothy Coppack (1) , Franz Bairlein (2)

1 Department of Ornithology
2 Institute of Avian Research "Vogelwarte Helgoland"

Bird migration has evolved under the influence of annual and daily fluctuations in resource availability. Numerous passerine migrants migrate exclusively by night, maximizing the time available for foraging and feeding during the day. When held in captivity, and in total absence of environmental cues, nocturnal migrants typically show rhythms of night-time restlessness (Zugunruhe), which persist with a periodicity of about 24 h. Experimental evidence suggests that these circadian rhythms of Zugunruhe may either result from a "redefinition" of the diurnal clock or from changes in the phase relationship between independent endogenous oscillators. The role of melatonin in this control system remains ambiguous. Lowered levels of circulating melatonin found during migratory nights could either be the positive stimulus, a permissive factor or a side effect of nocturnal wakefulness. Although the nutritional state of a migrant is known to strongly influence the incidence of migratory activity, the physiological link between the circadian clock controlling Zugunruhe and the metabolic/hormonal path-ways that regulate the incidence of migration is uncertain. A functional genetic approach promises to bring behavioural and physiological knowledge together. Determining the mechanisms that are involved in the day-to-day scheduling of migration is crucial for understanding the overall control of migration, as the sum of migratory nights determines for how long, and how far, a migrant potentially travels.

Mots clés: Circadian clock; Melatonin; Migratory restlessness; Photoperiod; Zugunruhe

Domaines: Biologie animale

Timothy Coppack, Franz Bairlein. Circadian control of nocturnal songbird migration. Journal für Ornithologie = Journal of Ornithology, 2011, 152 (S1), pp.67-73. ⟨10.1007/s10336-011-0708-z⟩. ⟨hal-00701726⟩