The Ruby-throated Hummingbird is the only species that regularly breeds in the eastern half of North America, making its presence in New England a distinct seasonal event. These small birds weigh only about three grams and possess a high metabolic rate that necessitates constant feeding. Their unique flight capabilities, including the ability to hover and fly backward, allow them to navigate tubular flowers for nectar and capture tiny insects. Because their survival depends on a reliable food supply, hummingbirds must migrate south when local resources decline.
The Critical Departure Timeline
The annual southward migration of the Ruby-throated Hummingbird from New England generally begins in late August and continues through September, sometimes extending into early October. This departure is a staggered process, where birds leave based on their age and sex. Adult males, whose reproductive duties are complete, are the first to depart and are typically gone from the region by the end of August.
Females and recently fledged juveniles follow the adult males, undertaking their southward journey throughout September. This second wave often causes a noticeable surge in activity at feeders and late-blooming flowers across the region. For most of New England, the majority of the local population has departed by the end of September.
Transient migrants passing through from areas farther north, such as Canada, continue appearing in the region well into the first two weeks of October. These late sightings are usually the final stragglers completing their journey.
Biological Triggers for Migration
The impulse to migrate is not triggered by a drop in temperature, but by an internal biological mechanism linked to the changing length of the day. This phenomenon, known as photoperiodism, means that the decreasing number of daylight hours in late summer acts as the cue for the birds. The shortening day length initiates a hormonal cascade that prepares the hummingbird’s body for the journey south.
This hormonal shift activates an instinctual feeding drive called hyperphagia, where the birds increase their food intake to build up fat reserves. Fat is the most energy-dense fuel source for migratory birds, and hummingbirds must accumulate enough to power a long, non-stop flight over the Gulf of Mexico. A typical Ruby-throated Hummingbird will nearly double its body weight by adding two to three grams of fat before departure.
The stored fat is metabolized during flight, providing more than twice the energy per gram compared to carbohydrates or protein. This fat-fueled metabolism also produces water as a byproduct, which helps prevent dehydration. Once the birds have reached this specific level of fat accumulation, they are ready to begin the migration, regardless of local weather conditions.
Supporting Hummingbirds During the Final Push
The period from late August through October is when human assistance can be most beneficial to migrating hummingbirds. A common misconception is that leaving feeders up too late will prevent migration, but departure is governed by photoperiod and fat reserves, not the presence of food. Maintaining clean and filled feeders ensures that both local birds and transients have the necessary fuel for their journey.
The standard nectar recipe of one part white granulated sugar to four parts water is the recommended concentration, as it closely mimics the sucrose content of natural flower nectar. Use only white sugar and water, avoiding honey, brown sugar, or artificial sweeteners, which can be harmful to the birds. Feeders should be cleaned every few days, especially during warm weather, to prevent the growth of mold or bacteria.
Because the last migrants and late visitors can appear through the first half of October, keeping feeders available until at least the end of that month is a helpful practice. This availability offers a final refueling opportunity for any birds delaying their departure due to weather or late development. By providing a consistent, clean, and appropriately mixed food source, people can directly support the incredible journey of these tiny, long-distance flyers.