The Rufous Hummingbird has the longest migration of any hummingbird, more than 5,000 miles a year. It flies from central Mexico to Alaska and back again. Hummingbirds migrate, not in flocks, but each one entirely alone. Males leave first followed by females several weeks later. On the south-bound journey the young leave last, flying alone on their first migration with no adult to guide them.
Predation accounts for most of the nest mortality.
Hummingbird mothers fearlessly attack hawks, crows, jays, chipmunks, snakes and even yellow jackets in defense of the eggs and young, but not always sucessfully. Accidents, high winds, cold, heavy rains, and heat, account for the remainder of fledgling deaths. Hummingbirds DO NOT migrate on the backs of geese. Migration has been thoroughly studied and each hummingbird migrates alone. Leaving feeder up too long will deter migration.