Birds, whether big or small, when flock together for long-haul flights, make V-formation which is not only fuel-efficient, but also affords them to periodically shift positions from front to the rear depending upon their tiring levels. The front is where you brave the winds most, while a rear position allows for some in-flight rest--a sort of semi-sleep state--due to the combined lift effect produced by the fellow birds ahead. This continues throughout the journey like a clockwork and every bird gets her fare share of rest. What a beauty!