The key physiological cue for migration could be the alterations inside the working day length. These improvements are relevant to hormonal alterations within the birds. During the period of time prior to migration, many birds Exhibit better action or Zugunruhe (German: migratory restlessness), very first explained by Johann Friedrich Naumann https://rafaelnlicu.bloggazza.com/36630067/the-2-minute-rule-for-pet-bird