The principal physiological cue for migration could be the variations inside the day duration. These changes are associated with hormonal adjustments in the birds. Within the period of time before migration, a lot of birds display better exercise or Zugunruhe (German: migratory restlessness), to start with described by Johann Friedrich https://beaulhqie.bloggip.com/37889826/5-easy-facts-about-pet-bird-care-uae-described