Hummingbirds, with their iridescent plumage and astonishing aerial acrobatics, captivate observers. These tiny birds, known for their rapid wingbeats and hovering flight, possess an energy level that defies their small stature. As colder weather approaches, a common question arises: where do these diminutive marvels go when winter arrives? The answer involves remarkable journeys and specialized adaptations that allow them to survive changing seasons.
The Annual Migration
Many hummingbird species across North America migrate to warmer regions for winter. This movement is driven by the decreasing availability of their main food sources—flower nectar and small insects—as temperatures drop and daylight hours shorten. Most hummingbirds in the United States and Canada journey south.
These migrations often span hundreds or thousands of miles. Many species, including the Ruby-throated Hummingbird, travel to Central America or Mexico for winter. Some Ruby-throated Hummingbirds even embark on a non-stop, 500-mile flight across the Gulf of Mexico, a journey taking 18-22 hours. The Rufous Hummingbird, breeding as far north as Alaska, undertakes one of the longest migrations for its size, covering nearly 4,000 miles to winter in southern Mexico.
Hummingbirds prepare for these flights by significantly increasing their body mass, often gaining 25-40% of their weight. They refuel frequently along their routes, stopping at locations with abundant food. Migration timing is influenced by changes in daylight duration, signaling to the birds when to depart. Males typically initiate the southward journey earlier than females, with juveniles following later in the season.
Winter Survival Mechanisms
Hummingbirds use physiological and behavioral adaptations to endure cold periods, both during migration and in wintering habitats. A primary survival mechanism is torpor, a state resembling deep sleep or mini-hibernation. When in torpor, their metabolic rate can decrease by as much as 95%, allowing them to consume up to 50 times less energy than when active.
During this state, a hummingbird’s body temperature can drop by nearly 50 degrees Fahrenheit, and its heart rate can slow from over 1,200 beats per minute to fewer than 50. This energy-saving strategy is typically used nightly, especially during cold weather or when food is scarce. Upon awakening, hummingbirds shiver their wing muscles to generate heat, gradually raising their body temperature over about 20 minutes before resuming normal activity.
Beyond torpor, hummingbirds adapt their foraging behavior and seek shelter to conserve warmth. They may eat more insects in winter, which provide essential nutrients when nectar is less available. Fluffing their feathers is another common behavior, creating an insulating layer of trapped warm air around their bodies. These combined strategies allow them to navigate the energetic demands of cold environments.
Hummingbirds That Overwinter
While most North American hummingbirds migrate, certain species and populations remain in temperate regions throughout winter. These “overwintering” hummingbirds demonstrate resilience and adaptability. The Anna’s Hummingbird is a key example, residing year-round along the Pacific Coast, from Southern California up to British Columbia and even parts of Alaska.
Anna’s Hummingbirds have expanded their range northward over recent decades, partly due to the proliferation of non-native flowering plants like eucalyptus and the widespread availability of human-provided feeders. These food sources offer sustenance when natural nectar is scarce. Anna’s Hummingbirds also consume more insects than many other hummingbird species, providing protein and fats during colder months.
Other species, such as some Rufous and Black-chinned Hummingbirds, have also been observed overwintering in parts of the southern United States, including the Gulf Coast and southwestern states like Arizona and California. Their ability to survive cold snaps is often attributed to their capacity for torpor and reliance on readily available food, including supplemental feeders. These instances highlight hummingbird adaptability, with some populations adjusting migratory patterns to take advantage of available resources in milder winter climates.