The principal physiological cue for migration is definitely the alterations while in the day length. These variations are connected with hormonal variations in the birds. In the time period prior to migration, several birds Screen larger exercise or Zugunruhe (German: migratory restlessness), 1st described by Johann Friedrich Naumann in 1795, https://portable-pet-water-bottle52973.tribunablog.com/the-5-second-trick-for-bird-52108379