The primary physiological cue for migration will be the adjustments within the day size. These changes are linked to hormonal modifications in the birds. In the period in advance of migration, several birds display bigger action or Zugunruhe (German: migratory restlessness), first explained by Johann Friedrich Naumann in 1795, in https://petshopdubai56555.therainblog.com/36459097/5-simple-techniques-for-getting-a-pet-bird-advice