Having to cross the Sahara in the middle of migration means a bird can’t count on food for some 5 nights of flying. So, how does a first-timer know to take on extra fuel?
For thrush nightingales traveling from Sweden to southern Africa, the cue for a life-saving eating binge may come from changes that birds sense in the magnetic field, propose Thord Fransson of the Swedish Museum of Natural History in Stockholm and his colleagues.