Hummingbirds are remarkable little birds that make epic migrations every year. Some species travel thousands of miles between their breeding grounds in North America and their wintering grounds in Mexico, Central America, and the Caribbean. This raises an interesting question – how do these tiny birds, some weighing less than a penny, rest and refuel during such long journeys?
Do hummingbirds sleep while migrating?
Yes, hummingbirds do sleep during migration flights. However, they have adapted to sleep while flying! A 2011 study published in Nature Communications found that migrating hummingbirds can sleep with half of their brain at a time. This phenomenon is called “unihemispheric sleep.” By keeping one half of the brain awake, hummingbirds can continue beating their wings and navigate during migration. The awake half of the brain also allows them to watch for predators and other threats.
How do hummingbirds sleep while flying?
Hummingbirds are able to sleep while flying due to the anatomy of their brains. Their brains have very little tissue connecting the two hemispheres. This allows one hemisphere to rest while the other stays awake. The eye connected to the resting hemisphere will also close. So a sleeping hummingbird will have one eye open and one eye closed while flying.
Researchers conducted experiments by capturing hummingbirds after migrating overnight and testing their brain waves. They found hemispheric sleep patterns showing one half of the brain asleep. When hummingbirds were kept awake by being placed in an unfamiliar cage, the brain wave patterns showed both hemispheres staying awake.
Why do hummingbirds need to sleep during migration?
Hummingbirds need to sleep during migration for a few key reasons:
- To prevent exhaustion – Migration flights can last overnight and require huge amounts of energy. Hummingbirds need to rest or they would become exhausted.
- To function properly – Sleep is vital for animals to function, including for memory, learning, and mood regulation.
- To avoid predators – By sleeping unihemispherically, hummingbirds can rest while still maintaining vigilance against any threats.
Where do hummingbirds stop to rest during migration?
During migration, hummingbirds make regular stops along the way to rest and refuel. Some key resting spots include:
Backyards
Hummingbird feeders and nectar-producing flowers in backyards provide an important source of food during migration. Hummingbirds will visit these spots repeatedly to tank up on energy.
orchards
Orchards with fruit trees give hummingbirds a place to rest and feed on fruit and insects. Citrus groves in particular attract hungry migrating hummingbirds.
Meadows and grasslands
Natural areas with diverse native wildflowers supply essential nectar for fuel. Hummingbirds use these extended rest stops to feed and sleep more deeply.
Riparian areas
Rivers, streams, and wetlands offer habitat for resting hummingbirds to find water, insects, sap, and sugar-rich tree flowers like maples and willows.
How long do hummingbirds rest during migration stops?
The length of time hummingbirds stop to rest depends on the needs of the individual bird. Brief rest stops may last just a few minutes as the hummingbird drinks nectar to reenergize. Overnight stops can last 12 hours or more as the hummingbird drinks, eats, and sleeps more deeply.
In one study, Rufous hummingbirds fitted with radio transmitters were found to stop for rest periods averaging about 2 days in spring and 3 days in fall during migration. The longer fall rest stops are likely to build up fat reserves before crossing the Gulf of Mexico, an 18-20 hour non-stop flight.
What are the differences between how smaller and larger hummingbirds rest?
| Smaller Hummingbirds | Larger Hummingbirds |
|---|---|
| Ruby-throated (3-4 grams) | Rufous (3-4 grams) |
| Make shorter migration trips (fly 500-2,000 miles one way) | Make longer migration trips (fly up to 5,000 miles one way) |
| Rest more frequently for shorter periods | Rest less often but for more extended periods |
| More able to refuel just from nectar sources | Refuel on nectar and small insects/tree sap |
| May be able to store enough fat for Gulf crossing nonstop | Require extended resting period before crossing Gulf of Mexico |
The differences in rest patterns relate to the different challenges faced by smaller and larger hummingbird species during migration. Larger hummingbirds like Rufous complete longer migrations of thousands of miles compared to smaller Ruby-throateds migrating hundreds of miles. The greater distances force larger hummingbirds to rest more substantially and build up fat reserves before big ocean crossings.
What food sources do hummingbirds seek out when resting during migration?
Hummingbirds require lots of energy in the form of sugar and calories to power their migration. When they stop to rest and refuel, they target food sources to meet their high energy needs, including:
Nectar
Flower nectar provides an immediate source of sugars that hummingbirds can quickly convert to energy. Native wildflowers and backyard feeders provide essential nectar.
Fruit
Some hummingbirds get extra sugars by eating small fruit including grapes, berries, and oranges when they are available.
Tree sap
Sapsucker woodpeckers drill holes in trees that fill with sap, creating a sweet treat used by hummingbirds.
Insects
Small spiders and insects provide fat and protein. Hummingbirds often hawk flying insects to add nutrition.
When do hummingbirds rest the most during migration?
The periods when hummingbirds rest the most during migration include:
- At night – Hummingbirds primarily migrate and rest during daylight hours. At night they conserve energy by entering torpor, a deep sleep state.
- Bad weather – Hummingbirds will take shelter and rest for extended periods when faced with heavy rain, winds, or storms.
- Before major water crossings – Hummingbirds preparing for a big nonstop flight over oceans, seas, or deserts will rest and feed for multiple days to store up fat.
- At major geographical barriers – Mountains ranges or other major geographical features require extra rest before crossing.
By taking advantage of long rest and refueling periods when possible, hummingbirds are able to sustain the incredible endurance challenge of migration.
Conclusion
The nonstop lifestyle of hummingbirds makes their seasonal migration an incredible feat. By resting and refueling strategically along their journey using adaptations like sleeping mid-flight, these energetic tiny birds complete some of the most amazing migrations in the animal kingdom. The next time you see hummingbirds zipping by, remember they are refueling to prepare for their extraordinary migratory journey.
