The Ruby-throated Hummingbird is the only species that breeds in North Carolina. Its annual journey south is a remarkable feat. These tiny birds, which weigh less than a nickel, follow an instinctual path thousands of miles from their nesting grounds. Their departure is not a single event, but a staggered, cyclical process, ensuring they reach their winter habitat before cold weather depletes their food sources.
Peak Migration Timing in North Carolina
The departure of Ruby-throated Hummingbirds begins in late summer and continues through the fall, following a pattern based on age and sex. Adult males, having completed reproductive duties, are the first to leave, starting their journey south as early as late July or the beginning of August. Most adult males have departed the state by mid-to-late September.
Adult females and the season’s young follow this first wave, generally migrating from late August through September. These juvenile birds are making their first migration, guided entirely by instinct, and are usually the last to depart. While the bulk of the population is gone by the end of September, stragglers may linger into early October. Regional variations exist, with birds in cooler mountain areas potentially departing earlier than those along the coast.
Biological Signals and Pre-Migration Preparation
The timing of departure is dictated by the photoperiod—the decreasing amount of daylight hours—rather than temperature or food availability. As summer transitions into fall, the shortening day length triggers hormonal changes, signaling the birds to begin preparations for the long-distance flight. This instinctual drive overrides external factors, such as the continued presence of a sugar feeder.
This internal signal initiates hyperphagia, a period of intense, non-stop feeding. During hyperphagia, hummingbirds dramatically increase their caloric intake, consuming large quantities of nectar and small insects to accumulate the necessary fuel. The goal is to build up fat reserves, which is the most efficient energy source for flight.
A migrating Ruby-throated Hummingbird may increase its body weight by 25 to 40 percent during this period, storing fat around organs and under the skin. This fat is essential because it provides more than twice the energy per gram than carbohydrates or protein. Its metabolic breakdown also produces water, helping to prevent dehydration during the journey.
Feeder Management and Common Misconceptions
A common concern is that leaving a sugar water feeder out too long will prevent hummingbirds from migrating. This is a misconception, as departure is governed by the light cycle, not food availability. The hormonal changes triggered by shortening days compel the bird to migrate, regardless of a full feeder.
Maintaining a clean and full feeder in the fall aids both resident birds preparing to leave and travelers passing through from the north. The concentrated energy source supports the intense fat-building phase of hyperphagia, providing reliable fuel when natural nectar sources may be dwindling.
It is recommended to keep feeders up in North Carolina until at least mid-to-late October. Remove them only after there has been an absence of hummingbird sightings for one to two weeks. This ensures that late-migrating juveniles or rare western vagrants, such as the Rufous Hummingbird, have a chance to refuel before continuing their journeys south.
The Southern Destination
After leaving North Carolina, Ruby-throated Hummingbirds head toward wintering grounds primarily located in southern Mexico and Central America, extending as far south as Panama. The journey demands utilization of the fat reserves built up during their time in North Carolina.
For many birds, the route involves a non-stop flight across the Gulf of Mexico, a distance of 500 miles or more. This journey is typically undertaken in a single stretch, requiring up to 20 hours of continuous flight. The stored fuel must be sufficient to power the entire journey before they can rest and feed again.