It's a month or two early to post about bird migration, particularly passerine migration, here in the northern hemisphere, but I did find this excellent review of the most recent science on the topic:
Birds that migrate at night enter a state of sleepless mania and gorge on foods by day, behaviors mediated by their biological clocks
Photo is our common Black and White Warbler, who will be passing through here, on the Atlantic Flyway, in May.