Hummingbirds are a fascinating group of birds found only in the Americas. They are known for their incredibly rapid wing beats, ability to hover in midair, and appetite for nectar. Hummingbirds have uniquely adapted physiological and behavioral strategies that allow them to meet their high energy demands from nectar while surviving in a variety of habitats and climates. An interesting question arises about how late in the year hummingbirds are able to find enough food before migrating or entering torpor. In this article, we will explore what is known about hummingbird feeding behavior and energetics late in the year.
Hummingbird feeding habits
Hummingbirds have the highest mass-specific metabolic rate of any vertebrate. To power their wings for flight, they consume up to eight times their own body weight in nectar every day. This reliance on carbohydrate-rich nectar is why hummingbirds are constantly visiting flowers in search of their next meal.
Hummingbirds use their slender, pointed bills to access nectar at the base of tubular flowers. Their tongues are forked with fringed tips that allow them to efficiently lap up nectar. Hummingbirds prefer flowers with higher concentrations of sucrose-dominated nectars. They reject nectars that are diluted by rain or contain high proportions of fructose.
In addition to nectar, hummingbirds consume small insects and spiders to obtain essential amino acids, vitamins, minerals, and fats. This reliance on insects supplements their nectar diet, especially during breeding when protein demands are higher.
Factors influencing late season feeding
Several factors influence the availability of flowers and insects that hummingbirds rely on later in the year:
Flowering cycles
Many flowers bloom in spring and summer when conditions are ideal for plant growth and pollinators are most active. Flower production declines in fall as daylight hours shorten and temperatures drop. However, some late-blooming flowers may provide food into autumn.
Migration and range
Most hummingbird species that breed in more northern latitudes migrate south for the winter. As blooms become scarce, they travel to warmer climates with more abundant flowers and insects. Species that reside year-round in the tropics and subtropics continue to find adequate food within their ranges.
Molt
Hummingbirds undergo an annual molt in late summer or early fall when they replace all their flight feathers. Molting is energetically expensive, so they require 20-40% more calories during this time. Good nutrition is essential for successful molt and survival.
Insect availability
Insects become less active and die off as temperatures drop in autumn. However, some hardy insects may still be available for hummingbirds to eat into late fall and winter.
How long do hummingbirds keep feeding?
The ability of hummingbirds to feed late into the year depends on a combination of factors:
Resident versus migrant species
In warmer southern regions, resident hummingbird species like Anna’s and rufous can feed year-round as long as some flowers or insects are available. Migrants that breed farther north require abundant late-season food to support pre-migratory fat storage.
Location
Areas with milder climates and a longer growing season sustain more late-blooming flowers. For example, the Pacific Northwest has bursts of fall flowers. At higher elevations, cooler weather brings earlier dormancy for plants.
Flora
Certain flowers and ornamental plants extend the nectar availability for hummingbirds. Sages, fuchsias, aloes, and autumn-blooming vines may flower into November or even December in some climates. Supplemental feeding from hummingbird feeders also elongates the season.
Weather patterns
Unseasonable cold snaps or early frost can abruptly end the flowering season and insect activity. Hummingbirds are forced to migrate sooner when food dies off quickly. However, warmer autumns allow them to stay and feed longer.
Here is a table summarizing the feeding duration for select hummingbird species:
| Species | Breeding Range | Migration Status | Typical Feeding Duration |
|---|---|---|---|
| Ruby-throated | Eastern US and Canada | Long-distance migrant | May – September |
| Rufous | Pacific Northwest, Canada, Alaska | Long-distance migrant | May – August |
| Allen’s | California | Short-distance migrant | March – November |
| Anna’s | West Coast, Southwest US | Resident | Year-round |
Strategies for late feeding
Hummingbirds have adaptations and behaviors to maximize their ability to feed as late into the year as possible:
Aggression
Dominant birds aggressively defend prime feeding territories with the most abundant nectar sources. Subordinates get squeezed out to suboptimal areas.
Torpor
Hummingbirds entering nightly torpor lower their metabolic rate and body temperature to conserve energy on cold nights when adequate nourishment is unavailable.
Fat storage
Pre-migratory hyperphagia allows hummingbirds to accumulate substantial fat reserves to fuel migration and sustain them when food is scarce en route.
Opportunistic feeding
Hummingbirds make the most of sporadic nectar supplies by constantly searching for any flowers or other carbohydrate sources. They gather at feeders when natural foods are hard to find.
Increased insectivory
Eating more insects helps hummingbirds get adequate protein in autumn when nectar is limited. They may glean dormant insects from foliage and bark.
Conclusion
Most hummingbird species can continue feeding well into autumn provided some flower or insect food resources remain available. However, freezing temperatures, plant dormancy, and declining insect activity eventually make it impossible for hummingbirds to meet their high metabolic demands. The exact end of the feeding season varies by species, location, and weather conditions each year. Hummingbirds have evolved a remarkable ability to take advantage of ephemeral late-season nutrition to fuel pre-migratory fattening or sustain resident populations. This allows them to thrive across a diverse array of habitats despite the constraints of their specialized nectar-feeding strategy. Careful observational studies and marking of individual birds are needed to continue elucidating differences in late-season feeding biology between hummingbird species and populations.
