Another facet of migration that seems to be inherently programmed is the diurnal pattern of activity. It is not simply that captive diurnally migrating species show migratory restlessness by day, and nocturnally migrating ones by night. The hour-to-hour patterns of restlessness seen in captive birds, whether day or night, match fairly precisely the hour-to-hour patterns of migration seen in the wild (for White-throated Sparrow Zonotrichia albicollis see MacMillan et al. 1970, for Reed Bunting Emberiza schoeniclus see Berthold 1978, for Goldfinch Carduelis carduelis see Glück 1978). This finding has been taken as another indication of endogenous control over the migratory process.
Throughout the year, diurnal migrants in captivity show a peak of activity in the morning and a smaller one in late afternoon, but at migration times these peaks are much more marked (e.g. Munro 2003). In addition, nocturnal migrants in captivity tend to become inactive in the afternoons before nights of migratory activity. They cease feeding about 2 hours before dusk, which in the wild would give time for the gut to empty before take-off (Ramenovsky et al. 2003). They go to roost in the normal way, and become active some time later. Low light intensity is necessary for a good display of nocturnal activity (Gwinner 1967).
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