Life SciencesPhysiologyZoologyCircadian RhythmsOrnithologyPhysiological EcologyCircadian Clock MechanismsCircadian EndocrinologyCircadian Gene ExpressionCircadian PhysiologyPhotoperiodic EndocrinologySeasonal PhysiologyCircadian PhotobiologyCircadian Rhythm AdaptationEndogenous Circannual RhythmsPhotoperiod RegulationPhotoperiodic AdaptationPhotoperiodic EntrainmentSeasonal Biology Of Vertebrates