The Ruby-throated Hummingbird is the only species that regularly breeds in Minnesota. These tiny birds, weighing less than a quarter of an ounce, undertake an astonishing migratory feat, traveling thousands of miles to reach their wintering grounds. Their departure begins in late summer and concludes as the first signs of autumn appear.
The Typical Departure Window
The southward migration of Ruby-throated Hummingbirds from Minnesota typically begins in mid-to-late August, following the conclusion of the breeding season. The first individuals to leave are the adult males, which often depart as early as the first week of August once the young fledge. They are followed by the adult females and the young of the year, which continue to feed and build up energy reserves for a few more weeks. The bulk of the population leaves in September.
Most hummingbirds have departed by the end of September, but sightings can still occur well into October. These later birds are often migrants passing through from breeding grounds further north in Canada. The last confirmed sightings usually dissipate by the first week of October.
What Triggers the Journey South
The signal prompting the hummingbirds’ journey south is the change in photoperiod, or the shortening of daylight hours, not a drop in temperature or a reduction in food availability. As the summer solstice passes, the decreasing duration of daylight initiates hormonal changes within the birds. This internal, biological clock ensures the hummingbirds begin their migration before colder weather sets in.
This environmental cue triggers a behavioral shift known as hyperphagia, an intense, prolonged period of feeding. The birds must rapidly accumulate fat, their efficient fuel source for migration. For instance, a 3-gram male hummingbird may gain 2 to 2.5 grams of fat, nearly doubling its body mass in preparation for the flight.
Preparing for the Long Flight
The intense feeding activity, or hyperphagia, is easily observed as the birds aggressively visit flowers and feeders in late summer. During this time, a hummingbird may consume its entire body weight in nectar and sugar water daily, along with up to 2,000 tiny insects. This feeding frenzy helps the birds store enough fat to fuel a flight of nearly 600 miles.
Observers should not worry that maintaining a feeder will prevent a hummingbird from leaving, as the photoperiod trigger is absolute. Leaving feeders available well into the fall provides much-needed fuel for Minnesota’s resident birds and for later migrants passing through from the north. Feeders should be kept clean and filled until at least one to two weeks after the last sighting has occurred.
The Southward Migration Route
The Ruby-throated Hummingbirds leaving Minnesota undertake a formidable journey, traveling an estimated 1,500 to 2,000 miles to reach their wintering grounds. Their final destination is typically Central America or southern Mexico, with some individuals flying as far south as Panama. The birds generally retrace the route they took north, following a broad path toward the Gulf of Mexico.
A significant portion of the population is believed to make a non-stop flight across the Gulf of Mexico, a distance of approximately 500 miles. This leg of the journey can take a single bird between 18 and 22 hours of continuous flight. Other individuals take a longer, safer coastal route, flying around the Gulf through Texas and northern Mexico before continuing south.