Hummingbirds are amazing little birds that have mastered the art of hovering flight. Their wings beat incredibly fast, allowing them to fly in any direction with precision and agility. But what exactly is the type of flight hummingbirds use to achieve this feat? Here we’ll explore the specifics of hummingbird flight and how their anatomy allows them to hover and fly backwards with ease.
Hovering Flight
Hummingbirds are the only birds that can truly hover in mid-air. Hovering is when a bird maintains a fixed position relative to the ground, flying into any headwinds without moving forward. This allows hummingbirds to stay stationary while feeding on flower nectar or inspecting their environment.
To hover, hummingbirds beat their wings in a figure-eight pattern. On the downstroke, the wings are angled slightly back, which generates the lift to keep the bird aloft. On the upstroke, the wings are angled forward to minimize drag. This asymmetrical stroke allows air to pass through the wings during both the downstroke and upstroke, creating consistent lift.
Hummingbirds beat their wings incredibly fast to generate enough lift for hovering. The average hummingbird wing speed is about 70 wing beats per second. To put that in perspective, houseflies beat their wings 200 times per second. The Ruby-throated Hummingbird has the fastest known wing beat at up to 200 beats per second!
Rapid wing beating is essential for hovering but requires a huge amount of energy. Hummingbirds have many anatomical adaptations that allow them to support this metabolically expensive style of flight.
Anatomical Adaptations for Hovering
Here are some key features that allow hummingbirds to hover efficiently:
- Lightweight skeleton – Hummingbird bones are thin and hollow, minimizing body weight.
- Powerful breast muscles – Up to 30% of their total body weight is flight muscle, the highest ratio of any bird.
- Rotating shoulders – Their shoulder joints can rotate a full 360 degrees allowing the wings to move in a full oval.
- Large heart – A hummingbird’s heart takes up about 2.5% of their body weight. They have the highest heartbeat rate of any animal.
- Effective oxygen use – Their muscles have a high density of capillaries and mitochondria to maximize oxygen utilization.
These specializations allow hummingbirds to generate enough lift to hover continuously. No other birds have evolved such complete adaptations for hovering flight.
Forward Flight
In addition to hovering, hummingbirds can fly swiftly in any direction, including backwards. Their forward flight speed averages around 25-30 mph but can reach up to 60 mph during courtship dives.
For forward flight, hummingbirds change their wing orientation and stroke pattern. Instead of a horizontal figure eight, they flap their wings back and forth similar to other birds. The upstroke and downstroke are mirrored, generating thrust on both. The rounded shape of the wing allows air to flow smoothly over the surface when flapped at high speeds.
By adjusting the angle of their wings and altering stroke patterns, hummingbirds can fly nimbly in any direction with great precision. Some species like the Anna’s Hummingbird have strips of stiff feathers along their wings that allow them to glide briefly between bursts of rapid flapping.
Backwards Flight
Hummingbirds are the only birds capable of sustained backward flight. This allows them to precisely maintain position while feeding without turning around.
To fly backwards, hummingbirds alter their wing angle on each stroke to reverse thrust. On the downstroke, the wings are oriented horizontally, generating forward thrust. On the upstroke, the wings rotate 180 degrees, providing reverse thrust. This asymmetrical motion allows them to propel themselves backward while still producing enough lift to stay airborne.
Hovering backwards takes an extreme amount of energy and is only done in short bursts. Anna’s Hummingbirds are the champions of backwards flight, using it frequently in their aerial courtship displays.
Maneuverability
The unique flight abilities of hummingbirds give them unmatched maneuverability in the air. Here are some of the aerial maneuvers hummingbirds can perform:
- Hovering – Maintaining a fixed position in air while expending enormous amounts of energy.
- Forward flight – Flying rapidly in any direction by flapping wings back and forth.
- Backwards flight – Generating reverse thrust on the upstroke to propel backwards.
- Rolling – Performing quick rolls and loops while flying by rapidly adjusting wing angles.
- Diving – Plunging downward at high speeds then pulling up rapidly.
- Inverted flying – Flipping upside-down and flying rapidly in reverse.
This combination of capabilities gives hummingbirds unrivaled flying skills. Their extreme maneuverability is used for defending territory, competing for mates, and evading predators.
Hovering in Wind
Hummingbirds are able to maintain a hover despite winds and gusts that would throw other birds off balance. Here’s how they do it:
- Rapid adjustments – Hummingbirds constantly alter the angle and speed of their wings to correct for wind shifts.
- Rotating shoulders – Allow the wings to modifiy stroke plane angle as needed.
- Side slipping – Turning their bodies parallel to the wind to minimize cross-section.
- Power reserves – Have enough power to increase wing stroke amplitude to generate more lift.
- Light bodies – Small size and light weight makes them less impacted by turbulence.
Hummingbirds are so adept at compensating for wind that they can continue feeding without moving when gusts blew other species sideways.
Slow Motion Hovering
Hummingbirds have the ability to hover in “slow motion” to conserve energy. During a slow hover, their wings beat much slower at around 10-15 strokes per second. This reduces the power required to hover by 27%.
However, very slow hovering near stall speed is unstable. Hummingbirds use their tail feathers like rudders to maintain controlled flight at these slow speeds. Tilting their tails left and right counters the yawing motion and keeps them centered in one spot.
Slow motion hovering is used during activities like roosting or incubating. It strikes a balance between staying aloft and conserving energy.
How Hummingbirds Hover in Place
Here is a summary of how hummingbirds are able to hover in place so effectively:
- Figure-eight wing motion generates lift on both downstroke and upstroke.
- Wings beat at high frequencies up to 200 flaps per second.
- Specialized anatomy maximizes power output and efficiency.
- Rapid adjustments allow them to compensate for wind and stay fixed in space.
- Slow motion hovering conserves energy when a stable position is maintained.
No other birds exhibit such a complete mastery of sustained hovering flight. This gives hummingbirds exclusive access to energy-rich food sources that cannot be exploited by other species.
Hovering Flight Advantages
Here are some key advantages hummingbirds derive from being able to hover:
- Feed while stationary – Can draw nectar from flowers without moving.
- Conserve energy – Hovering takes less energy than flapping constantly.
- View surroundings – Excellent observation platform for spotting food, mates, or predators.
- Defined territories – Helps establish and defend highly localized territories.
- Mating displays – Impressive hovering ability signals fitness to potential mates.
- Unmatched agility – Ability to fly in any direction from a standstill enables precise maneuvers.
Hovering flight gives hummingbirds access to food not reachable by other species. It also enables aerial displays for courtship and competition. The maneuverability provides an advantage in evading predators and intruders.
Metabolic Cost of Hovering
Hovering flight requires an immense amount of energy to generate enough lift to stay airborne. Here are some figures that illustrate the high metabolic cost of hovering for hummingbirds:
- Heart rate up to 1,200 bpm while hovering, compared to around 500 bpm while perched.
- Oxygen consumption rises to 10-15 mL O2/gram of tissue while hovering. For comparison, human athletes max out at around 1 mL/gram.
- Hummingbirds burn fat reserves rapidly and may starve after just a few hours without food.
- The metabolic rate required for hovering is the highest known for any animal on a per gram basis.
To meet these extreme energy demands, hummingbirds have evolved supercharged physiological systems. But despite their specializations, they cannot hover for extended periods and must stop to rest periodically.
Differences Between Hummingbird Species
There are over 300 different hummingbird species. Here are some ways their hovering and flying abilities differ:
Species | Wing beat rate (flaps/second) | Heart rate while hovering (bpm) | Notes |
---|---|---|---|
Anna’s Hummingbird | 62 | 1,200 | One of the most agile species, excellent at backward flight |
Ruby-throated Hummingbird | 53 | 1,200 | The only breeding hummingbird in Eastern North America |
Rufous Hummingbird | 55 | 1,000 | Smallest hummingbird species at just 3 grams |
Giant Hummingbird | 12 | 250 | Largest species – can weigh up to 24 grams |
As these examples illustrate, smaller hummingbird species tend to have faster wing beats and a higher heart rate while hovering. Larger species hover more slowly due to their greater body mass.
Hovering in Hummingbird Courtship
Hovering capability plays an important role in hummingbird courtship. Male hummingbirds perform elaborate hovering displays to impress females. Here are some courtship behaviors that involve hovering:
- Stationary hover – Male maintains a fixed hover in front of female.
- Dive displays – Male ascends rapidly then dives past female in a blur.
- Aerial maneuvers – Male flies in loops and arcs around the female while hovering.
- Shuttling – Male flies back and forth horizontally past the female at high speed.
- Role reversal – Female will sometimes perform her own hover display in response.
These remarkable hovering feats demonstrate the male’s fitness and flying skills. Females watch the displays to assess a potential mate. Better hovering ability indicates genetic strength that will be passed to offspring.
Evolution of Hummingbird Hovering
Hovering flight evolved in hummingbirds over millions of years. Some researchers theorize that it initially developed through the following stages:
- Gliding – Primitive hummingbirds evolved from swift-like ancestors that were adept gliders but could not hover.
- Increased maneuverability – Direction changes while gliding improved, allowing more controlled flight.
- Partial hovering – Hummingbirds learned to hover briefly, first by flexing their tails then through wing modifications.
- Sustained hovering – Aerodynamics and physiology adapted to enable extended hovering.
- Agile hovering – Advanced control and aerial maneuvers evolved to maximize flight capabilities.
Each stage provided an advantage that was passed down over generations. Sustained hovering gave access to new nectar sources, driving specialized adaptation through natural selection.
Hovering in Other Animal Species
A few other animals have evolved the ability to hover for short durations, but none come close to matching the embodiment of hummingbirds. Examples include:
- Insects – Flies, bees, and dragonflies can hover by beating translucent wings at high frequencies. But they lack the anatomy for extended hovering.
- Nectar bats – Some bats like the lesser long-nosed bat can briefly hover at flowers to lick nectar.
- Kestrels – These small falcons sometimes hover briefly when hunting, but most hunting is done on the wing.
Hummingbirds are truly in a league of their own when it comes to specialized adaptations for sustained hovering flight. No other warm-blooded vertebrate can match their perfect balance of anatomy, aerodynamics, and energy output.
Conclusion
In summary, hummingbirds are capable of multiple forms of specialized flight:
- Precise hovering in place by rapidly beating wings in a figure-eight pattern.
- Agile forward flight in any direction by changing wing orientation.
- Backward flight by reversing wing thrust on each upstroke.
- Extreme aerial maneuvers like upside down flying, rolls, and dives.
This gives them unmatched flying abilities. Hovering provides hummingbirds exclusive access to nectar sources not available to other birds. It also enables energy-intensive display behaviors used in mating. Hummingbird flight is one of the marvels of the natural world.