Birds do fly at night, and are able to fly in cloud, although probably not for long periods of time.
Large species of vultures (Gyps) can be seen at altitudes of around 10-15000ft.
Ruppels Vulture Gyps rueppellii holds the record for high flying - more than 37000ft. (Bird Migration By Thomas Alerstam, David A. Christie, Astrid Ulfstrand - Cambridge University Press)
This vulture is generally seen in the regions of central Africa.
Species of ducks, geese and swan and waders are examples of long distance migratory birds.