Hummingbirds are a captivating sight in Pennsylvania during warmer months, with iridescent colors and rapid wingbeats. As summer fades and autumn approaches, these tiny birds seem to vanish, prompting questions about their whereabouts. Their disappearance each fall marks the beginning of an annual journey, a testament to their endurance and navigational abilities.
The Southern Migration
The Ruby-throated Hummingbird, the primary species found in Pennsylvania, undertakes a significant migration southward to escape colder temperatures and dwindling food sources. Most winter in southern Mexico and Central America, extending as far south as Panama. Some individuals may winter along the U.S. Gulf Coast or in southern Florida.
Departure from Pennsylvania typically begins in late August or early September, though some are observed into October. Males often initiate this journey earlier than females. Their migration route takes them thousands of miles.
A significant portion of the population crosses the Gulf of Mexico, a non-stop flight of approximately 500 miles taking 18 to 22 hours. Other hummingbirds opt for an overland route, following the coastline. Despite their small size, these birds can maintain average flight speeds of 20 to 30 miles per hour.
Preparing for the Journey
To fuel this demanding migration, Ruby-throated Hummingbirds undergo significant physiological changes. They enter a period of intensive feeding, known as hyperphagia, consuming large quantities of nectar and insects to build energy reserves. During this time, they can gain 25 to 40 percent of their body weight, with some individuals even doubling it. This accumulated fat serves as the primary fuel source for their long flights.
Their tiny bodies possess a high metabolism, allowing their hearts to beat up to 1,260 times per minute and their wings to flap between 15 and 80 times per second during flight. To conserve energy, especially overnight, hummingbirds can enter a state of torpor. This involves lowering their body temperature and significantly reducing their metabolic rate, sometimes by as much as 95 percent.
Migration is guided by instinct, triggered by environmental cues like changes in daylight hours and decreasing food availability. Hummingbirds typically migrate alone, often following the same migratory paths year after year. Even young birds, on their first migration, navigate these extensive routes without parental guidance. They fly during the day when nectar sources are abundant, often flying low enough to spot food along their path.
The Spring Homecoming
After wintering in warmer climates, Ruby-throated Hummingbirds begin their northward journey back to Pennsylvania. The first arrivals, usually males, can be seen in southern Pennsylvania around mid-April, becoming more widespread in northern areas by early May. Females typically follow a week or two behind the males.
This return migration is also instinctual, precisely timed to coincide with the resurgence of blooming flowers and the availability of insects in their breeding grounds. Many hummingbirds exhibit a strong fidelity to their breeding sites, returning to the same areas each spring. Their arrival marks the completion of their annual migratory cycle, bringing these birds back to the landscapes where they raise their young.