Passerine MigrationMost birds cannot cover the distance between their breeding and winter quarters in one hop. They have to make multiple flights alternated with stopovers. Which factors govern the birds decisions to stop, to stop for how long, when to resume flight? What is better to accumulate much fuel and to make long flights for many hundreds of kilometres, or to travel in small steps? Is it necessary to find habitats similar to the breeding ones or other habitats