Endogenous control of migration and calendar effects in an intratropical migrant, the yellow-green vireo

摘要: Abstract Endogenous circannual rhythms control the time course for moult, migratory fattening and autumn migration in juveniles of several bird species that breed temperate zone. Exogenous factors, such as daylength, can also exert a measure control: photoperiodic cues detected by birds hatch late season induce accelerated juvenile development, assuring late-hatched young migrate at same early-hatched young. Whether these mechanisms apply to between breeding nonbreeding areas entirely within tropics latitudes characterized little seasonal variation photoperiod is unknown. We conducted common-garden experiment Panama (9°N) which we hand-reared wild-caught nestling yellow-green vireos, Vireo flavoviridis , under constant monitored them expression activity. Even absence cue, moulted, accumulated fat reserves initiated activity, suggesting endogenous processes. Age onset activity were each significantly negatively correlated with date, however, so three processes was synchronized among respect season. suggest slight differences daylength perceived either nestlings themselves short before they collected (at 6–8 days age) or adult females during egg production influenced rate thus allowing later-hatched accumulate younger age than Remarkably, differed earliest latest dates this study only 33 min.