Circannual basis of geographically distinct bird schedules.

@article{Helm2009CircannualBO,
  title={Circannual basis of geographically distinct bird schedules.},
  author={Barbara Helm and Ingrid Schwabl and Eberhard Gwinner},
  journal={The Journal of experimental biology},
  year={2009},
  volume={212 Pt 9},
  pages={1259-69}
}
To anticipate seasonal change, organisms schedule their annual activities by using calendrical cues like photoperiod. The use of cues must be fitted to local conditions because schedules differ between species and habitats. In complete absence of temporal information, many species show persistent circannual cycles that are synchronised, but not driven, by photoperiod. The contribution of circannual rhythms to timing under natural photoperiodic conditions is still unclear. In a suite of… CONTINUE READING