Hummingbirds are amazing little birds that capture our imagination. Their ability to hover midair and fly backwards sets them apart from other birds. These unique flying skills allow hummingbirds to get nectar from flowers that other birds can’t. Another thing that makes hummingbirds special is their migratory habits. Many hummingbird species migrate long distances every year, some traveling over 2,000 miles between their summer and winter homes. This raises an interesting question – do hummingbirds fatten up before making their long migratory journeys? In this article, we’ll take a closer look at hummingbird migration and whether these tiny birds bulk up with extra fat reserves to fuel their travels. Understanding more about hummingbird migration gives us insight into the lives of these remarkable creatures.
The migratory habits of hummingbirds
Hummingbirds are found only in the Americas. Of the over 300 different hummingbird species, most are permanent residents that don’t migrate. However, some undertake amazing migrations covering huge distances every year. For example, the rufous hummingbird breeds in the northwestern United States and Canada during the summer. When winter approaches, it migrates down to Mexico and even as far as Panama for the winter. The rufous hummingbird migrates a whopping 3,900 miles each way!
Other long-distance migratory hummingbirds include Allen’s hummingbird and the ruby-throated hummingbird. Their migration is driven by the need to find food and suitable breeding habitats. Flowering plants that provide nectar are more abundant during the summer in the northern regions. As winter approaches and flowers become scarce, the birds fly south to warmer climates where they can continue finding food. This allows hummingbirds to breed and thrive both in the north during summer and south during winter. Their excellent flying skills make these long-distance seasonal migrations possible.
Do hummingbirds gain weight before migrating?
Given the enormous distances hummingbirds can fly during migration, it raises a question about how they prepare for their long journeys. Do hummingbirds intentionally put on extra weight in fat reserves to help fuel migration? There is some evidence that hummingbirds do increase their fat stores prior to migration:
Higher fat scores before migration
Researchers have captured hummingbirds right before migration and analyzed their fat reserves. They use a fat scoring system to estimate the amount of fat by looking at fat deposits in certain areas like the furcula and abdomen. Studies have found that hummingbirds have higher fat scores right before migration compared to during the breeding season. One study found female rufous hummingbirds had average fat scores of 2.7 out of 5 before migrating, indicating moderately high fat levels.
Increased food consumption
Experiments that provide captive hummingbirds with unlimited food found they will increase their food intake dramatically leading up to migration. For example, one study found rufous hummingbirds doubled their food consumption to an average of 38% of their body mass per day just before migration. This overeating in the weeks before migration suggests the birds are intentionally bulking up.
Heavier body mass
Researchers have compared the body mass of hummingbirds right before and after migration. One detailed study of ruby-throated hummingbirds compared their pre-migratory weights in August to post-migratory weights in May. They found the birds were over 15% heavier pre-migration. Across 15 species, hummingbirds gain an average of 40% in body mass before migration begins through increased fat and food stores.
How much fat do they need to migrate?
The fact that hummingbirds increase their fat reserves and weight leading up to migration suggests they require substantial energy to complete their journeys. But just how much fat reserve does a tiny hummingbird need to migrate hundreds or thousands of miles?
Researchers have estimated that hummingbirds require fat stores equal to about 50% of their body weight to complete migration. For a typical 4 gram ruby-throated hummingbird, that would be around 2 grams of fat, or equivalent to over 4,000 calories of energy. That may not seem like much, but for their small size it represents a huge amount of energy.
This fat provides enough fuel to allow hummingbirds to fly around 6-10 hours nonstop or cover 500 miles without needing to stop and refuel. However, hummingbirds don’t always make the trip in one continuous flight. They stop periodically to rest and feed for a few days before resuming migration. This allows them to replenish some fat reserves before the next leg of their journey. Careful management of their fat stores is crucial for hummingbirds to complete their long migrations.
Other ways hummingbirds prepare for migration
While bulking up on fat stores is important, hummingbirds also prepare for migration in other ways:
Muscle building
Hummingbirds will increase the size of their pectoral muscles leading up to migration. The pectorals are the main muscles powering their flight. Enlarging these muscles provides more power for sustained hovering and flapping needed during migration.
Reproductive changes
Hummingbirds undergo reproductive changes before migration that may help maximize their chances of successfully migrating. In males, the testes decrease in size while in females, the ovaries and oviduct regress. This probably reduces energy demands that would otherwise be required for reproduction, allowing more energy to be focused towards migration.
Moult and orientation
Hummingbirds will complete their annual molt (replacing feathers) prior to migration. This ensures their plumage is in good shape for the journey. They also may orient themselves in the direction of migration and practice migratory restlessness or “Zugunruhe” before departing.
What do hummingbirds eat along migration routes?
While adequate fat reserves are crucial, hummingbirds also need to refuel during migration by finding nutritious food sources along their route. Here are some of the main things hummingbirds feed on during migration:
Tree sap
Hummingbirds can obtain sap by piercing holes in tree bark with their bills. Tree sap is an excellent source of sugars that provide quick energy. Some favorite sap sources are birches, maples, willows and hemlocks.
Nectar
Hummingbirds rely heavily on flower nectar to fuel migration. They prefer red tubular flowers like bee balm, cardinal flower and trumpet vine that are high in sugars. Gardens and feeders provided nectar as well.
Insects
Hummingbirds get essential proteins and nutrients by eating small insects and spiders. They pluck these prey items from leaves, branches and even snatch them out of the air.
Having networks of suitable stopover habitats along migration routes that provide these food sources is crucial for hummingbird migration success and survival. Nature preserves and backyard habitats that offer nectar plants and insects help sustain migrating hummingbirds.
How long does hummingbird migration take?
The time it takes hummingbirds to complete migration depends on a few key factors:
Distance travelled
The further the migration route, the longer it takes to complete of course. Shorter migrations of a few hundred miles may take only a week or two, while long-distance migrations of a couple thousand miles can take a month or longer.
Terrain
Migrating over large ecological barriers like seas, deserts and mountains increases the time and energy required compared to open habitats. For example, the ruby-throated hummingbird flies across the Gulf of Mexico nonstop, which takes extra time.
Weather
Hummingbirds avoid migrating during periods of high winds, precipitation or other inclement weather. Bad weather causes them to pause migration and seek shelter which lengthens the duration of the overall journey.
Stopovers
How often a hummingbird stops to rest and refuel impacts migration duration. Frequent lengthy stopovers to rebuild energy reserves lengthen the time to reach the final destination. Young birds on their first migration tend to make more frequent stops.
On average, most hummingbirds complete migration in 1-2 months. But some individuals may stagger along the route for up to 5 months! There is high variability depending on the particular challenges each bird faces.
Do hummingbirds migrate alone or in groups?
When we picture bird migration, we often envision large flocks traveling together. But hummingbirds are primarily solitary migrants that each make the journey on their own rather than in groups or flocks. There are a few reasons why hummingbirds migrate solo:
Limited social structure
Hummingbirds don’t have a strong social structure outside of mating. They don’t form long-term pair bonds or family groups that move together. The solo lifestyle doesn’t facilitate migrating together.
Lack of leadership
Social migrating birds often have older, experienced individuals that lead migration and guide younger birds. Hummingbirds don’t have this leadership element.
Competition
Hummingbirds can be highly territorial and competitive over food resources. Migrating in groups may increase conflict over limited stopover food supplies. Solitary travel helps reduce competition with other hummingbirds.
Predator avoidance
Smaller groups or single birds may be less conspicuous to predators like hawks and falcons during migration. There may be a survival advantage to migrating alone.
However, occasionally sizable groups of hummingbirds may converge in prime stopover habitats with abundant food. So while they primarily migrate solo, hummingbirds may briefly gather in migratory hotspots before dispersing again to continue their solitary journeys.
How do hummingbirds navigate during migration?
One of the most astonishing things about hummingbird migration is how these tiny birds can navigate over hundreds or thousands of miles to find the same breeding and wintering sites year after year. They manage this incredible feat through a combination of navigation strategies:
Celestial cues
Hummingbirds appear able to use the position of the sun, stars and other celestial objects to orient themselves in the proper direction during migration. This provides a consistent large-scale guide for navigation.
Landscape features
Prominent landscape features like coastlines, rivers, mountain ranges and valleys provide important visual cues that help guide hummingbirds along established migration routes.
Magnetoreception
Some evidence suggests hummingbirds may sense the Earth’s magnetic field through an internal compass-like system and use this information to gauge direction. Other birds are known to perceive magnetic fields for navigation.
Memory
Adult hummingbirds rely heavily on learning and remembering landmarks and routes from previous migrations. Their excellent memory allows fidelity to the same breeding and wintering sites each year.
Smell
Hummingbirds may use their keen sense of smell to locate favorable stopover habitats with flowers along migration routes. Odors provide useful geographic cues.
The combination of these advanced sensory capabilities and mental mapping allows hummingbirds to successfully navigate their migratory journeys year after year even over thousands of miles.
Are hummingbird migration patterns changing?
Like many birds, hummingbirds are facing threats from climate change, habitat loss and other environmental impacts that may disrupt their migration in the future. Here are some potential ways hummingbird migration could change:
Shifting timing
The exact timing of when hummingbirds migrate appears to be shifting earlier in spring and later in fall compared to historical patterns, possibly in response to warming temperatures.
Altered routes
Habitat changes such as deforestation of wooded stopover sites may force hummingbirds to alter migration routes to find alternative rest stop locations.
Expanded ranges
Some hummingbird species like the rufous hummingbird appear to be expanding their breeding ranges farther north in response to warmer temperatures. This can lengthen their overall migration distance.
More wintering in U.S.
There are increasing overwintering reports of species like Anna’s and rufous hummingbirds in the southern U.S. Higher winter temperatures allow them to survive without migrating to Mexico.
Population declines
Loss of food sources along migration routes and threats like building collisions may contribute to declines in some hummingbird populations that migrate long distances.
Continued monitoring of hummingbird migration is important to track how they are responding to environmental changes and identify ways we can help sustain migratory hummingbird populations. Providing hummingbird-friendly habitats along their migration routes is one way the public can make a difference.
Amazing facts about hummingbird migration
To wrap up, here are few incredible facts about the phenomenon of hummingbird migration:
– Ruby-throated hummingbirds can fly nonstop over the Gulf of Mexico, a 500+ mile journey.
– Hummingbirds double their heart rate up to an astonishing 1,260 beats per minute during migration.
– The rufous hummingbird migrates farther than any other hummingbird species, with a one-way trip up to 3,900 miles.
– Hummingbirds prefer to migrate on sunny days with tailwinds that help push them along.
– Young hummingbirds on their first migration have zero prior experience. Their navigation is driven purely by instinct.
– Hummingbirds migrate surprisingly fast, cruising up to 30 miles per hour when conditions are right.
– Hummingbird migrations dates back thousands of years. Scientists have found ancient hummingbird fossils along prehistoric migration routes.
The long journeys and unique adaptations of hummingbirds make their biannual migrations one of nature’s most incredible phenomena. Increased understanding of how and why hummingbirds migrate gives us appreciation and insight into the lives of these captivating creatures. Plus it allows us to better protect and sustain hummingbird populations undertaking their epic seasonal voyages across the Americas.
Conclusion
In conclusion, research shows that most hummingbirds do intentionally fatten up before migrating. They increase food intake substantially in the weeks beforehand, resulting in higher fat stores and heavier body mass to provide extra energy reserves. This fat can allow them to fly 6-10 hours nonstop and cover hundreds of miles without refueling. Hummingbirds may double their normal body fat content prior to migration.
While fattening up is important, hummingbirds also prepare in other ways like enlarging flight muscles, altering reproduction and completing molts beforehand. During the migration journey itself, they require networks of stopover habitats that provide food sources like nectar and insects to refuel along the way. While exact migration patterns, timing and duration vary across species and geography, most hummingbirds complete their seasonal journey in 1-2 months.
These long-distance migratory champions navigate using cues like the sun, stars, magnetoreception and memory. Their incredible migrations may be shifting and facing new threats from climate and habitat changes. Continued conservation efforts are needed to sustain hummingbird populations throughout their migratory ranges. By understanding the phenomenon of hummingbird migration, we gain deeper appreciation of the tenacity and brilliance of these ultra-long distance avian globetrotters.
