There are a few types of birds that have the unique ability to fly backwards. This goes against what we typically think of when it comes to avian flight, as most birds only fly forwards. However, certain species have developed specialized skills that allow them to defy gravity and common sense by flying in reverse.
Examples of Birds That Can Fly Backwards
Here are some of the most noteworthy birds that are able to achieve backwards flight:
- Hummingbirds
- Kingfishers
- Northern Flickers
- Nuthatches
- Chimney Swifts
Of these, hummingbirds are probably the most iconic example. Their ability to hover and dart backwards on a dime seems almost supernatural. Read on to learn more about how certain avian anatomies make reverse flight possible.
How Do Birds Fly Backwards?
For most birds, forward flight is achieved through the synchronized movement of their wings. The wings move in a figure-eight pattern that pushes air under the wing during the downstroke, generating lift and thrust to propel the bird forward. However, birds that can fly backwards generate reverse thrust by altering their wing motion.
Two key adaptations allow certain species to achieve this:
- The ability to rotate their wings forward or backward during the upstroke
- Asymmetrical tail feathers that provide thrust
By flapping their wings forward on the upstroke and backward on the downstroke, these birds can maintain lift while generating rearward thrust. The fanned tail also contributes additional backward push with each wingbeat.
Hummingbirds
Hummingbirds are expert hoverers and the only bird group able to fly backwards. They can beat their wings up to 80 times per second and rotate them in a full circle. Their flying skills are unrivaled in the bird world.
While hummingbirds sometimes use reverse flight to back away from feeders or flowers, they more commonly utilize it for mating displays. Males will fly backwards in an inverted loop to impress females.
Kingfishers
Belonging to the family Alcedinidae, kingfishers are medium-sized birds that inhabit rivers and coastlines across the globe. They typically perch on branches hanging over the water and dive headfirst to catch fish.
Part of what enables their plunging dives is the ability to fly backwards from their perches. Kingfishers beat their wings forward on the upstroke and backward on the downstroke, allowing them to launch into a controlled backward dive with ease.
Northern Flickers
Northern flickers are large woodpeckers found throughout forests in North America. While they spend most of their time clinging to tree trunks, they occasionally take short backward flights between trees.
Like other woodpeckers, flickers have unusually long, pointed tail feathers that they use as props when climbing. These tails can also provide rearward thrust to initiate quick backward flights over short distances.
Nuthatches
Also adept climbers, nuthatches move up, down, and sideways across tree bark with ease. Their long claws help grip the bark, while their short tails help keep them balanced. While headfirst downward climbing is their specialty, they can also fly backwards off of tree trunks.
To achieve this, nuthatches alter their wing motion so the wings are pushed forward on the upstroke and swept backward on the downstroke. The downward curve of their bill may also improve their aerodynamics for reverse flight.
Chimney Swifts
Lastly, chimney swifts are one of the few birds capable of sustained backward flight. They sometimes enter chimneys or hollow trees backwards by flying in reverse into the opening. Chimney swifts beat their long, curved wings forward on the upstroke and backward on the downstroke.
Their tail bristles, which protrude beyond the end of the tail, may provide some rearward thrust. But sustained backward flight in chimney swifts likely relies more on specialized wing motion than tail anatomy.
Why Fly Backwards?
For most birds that demonstrate reverse flight abilities, this unique skill serves specific purposes:
- Courtship displays (hummingbirds)
- Improved maneuverability in dense habitats
- Ease of landing on vertical surfaces (woodpeckers, nuthatches)
- Precision diving and hunting (kingfishers)
- Accessing cavities and nesting sites (chimney swifts)
Backward flight allows these species to exploit ecological niches that would otherwise be unavailable. Hummingbirds wouldn’t be able to hover and feed from flowers without the ability to fly backwards. Kingfishers would be forced to find alternative nesting and hunting strategies if they could only fly head-on.
In most cases, reverse flight provides an advantage in food-getting, courtship, or access to shelter. It’s no wonder this ability has evolved independently in multiple unrelated bird groups.
Comparative Anatomy
Backward-flying birds vary widely in size, habitat, diet, and taxonomy. Here is a comparison of anatomical adaptations across some of the major groups:
| Species | Wing Anatomy | Tail Anatomy |
|---|---|---|
| Hummingbirds | Short, high aspect ratio wings enable rotation | Small, forked tail |
| Kingfishers | Long, broad wings provide lift | Large, wide tail acts like a rudder |
| Woodpeckers | Long primary feathers facilitate backwards stroke | Stiff, pointed tail feathers act as a prop |
| Nuthatches | Short, rounded wings permit reversed motion | Short tail improves balance and control |
| Chimney Swifts | Long, curved wings optimized for flapping flight | Short tail with protruding bristles |
As evidenced by this table, specialized wings that can rotate at the shoulder joint are essential for backwards flight. Tail shape also plays an important role, providing rearward thrust in many of these species.
Neural Control of Flight
A key question surrounding backward flight is how birds are able to neurally control and coordinate this complex physical task. There are a few possibilities:
- Symmetry in the brain’s motor centers allows easy switching between forward and backward wing motions.
- Hummingbirds may have clusters of neurons dedicated specifically to controllingbackward flight.
- Visual input is used to fine-tune direction during reversed flight.
Researchers hypothesize that hummingbirds and other backwards-flying species have some asymmetry between the right and left sides of motor regions in their brains. This allows them to activate different sides to control forward versus backward wing movement.
There is also evidence that hummingbirds have evolved unique neural wiring to handle the demands of sustained backward flight. It seems controlling reversed hovering and rapid maneuvers requires specialized circuits in their brains.
Finally, backwards-flying birds likely rely heavily on visual information to control their direction. Proprioceptive feedback from the wings is disrupted during reversed flight, so they may use sight to make aerodynamic adjustments.
Flight Aerodynamics
The physics of backwards bird flight provides an interesting look at low-speed aerodynamics. Lift must equal the bird’s weight in order to hover, regardless of direction. But what are the aerodynamic mechanisms at play?
Here are some key elements of reverse flight aerodynamics:
- Drag likely replaces steady forward thrust during backflight.
- Flapping wings can produce reverse thrust by altering angle of attack.
- Rapid rotation of the wings is key for producing lift and drag bidirectionally.
- Tails provide rearward thrust in addition to the flapping wings.
Research shows that for hummingbirds, their wing rotation allows the angle of attack to stay consistent throughout the downstroke and upstroke. This lets them generate lift in either direction. Drag replaces thrust as their primary rearward force.
The angle of attack also shifts dynamically along the length of the wings through each stroke. This lets hummingbirds control torques and forces for stability in diverse flight modes.
Additionally, the tail operates like a low-aspect ratio wing. It provides lift and drag that enhances maneuverability. This allows tailless hummingbirds to still fly backwards, but with reduced performance.
Evolution of Backward Flight
The ability to fly backwards evolved independently in several different lineages of birds. This suggests there were separate selection pressures driving the development of reverse flight. Here are some possible evolutionary pathways:
- Hummingbirds evolved from swifts, which display some elements of reversed flight.
- Kingfishers’ plunge-diving strategy favored the ability to fly backwards.
- Woodpeckers benefited from rearward launch while clinging to trunks.
- In nuthatches, backwards flight improved trunk-climbing mobility.
- Ancestral swifts likely used backflight to access nesting cavities.
In hummingbirds, the ability to fly backwards stemmed from the demands of sustained hovering. Their ancestor species were likely swifts that used primitive forms of reversed flight during aerial pursuits.
For kingfishers, the precision required for plunge-diving from branches above water selected for enhanced maneuverability. Backward takeoff gave them greater diving control.
In woodpeckers and nuthatches, rearward flight evolved to facilitate movement in complex arboreal habitats. For chimney swifts, it improved access to enclosed nesting sites in trees and caves.
Conclusion
The rare ability to fly backwards sets hummingbirds, kingfishers, woodpeckers, nuthatches, and swifts apart from other avian species. Their specialized wing and tail anatomy enables unique aerodynamic maneuvers that most birds simply cannot perform.
While uncommon in the broader context of avian diversity, reverse flight provides essential ecological benefits to the species that possess it. Being able to fly backwards allows these birds to thrive in their preferred habitats and fill specific niches.
Understanding the mechanics, neural control, and evolution of backwards flight reveals fascinating insights into bird anatomy, physiology, and natural history. The next time you see a hummingbird zip backwards away from a feeder, appreciate that you are witnessing an extraordinary aeronautical feat!
Summary
The following are key points about birds that can fly backwards:
- A few types of birds, including hummingbirds, kingfishers, and nuthatches, can achieve reverse flight.
- Specialized wing and tail anatomy enables backward thrust and maneuverability.
- Reasons for backwards flight include courtship, improved hunting, and accessing cavities.
- Wing rotation, drag, and tail surfaces contribute to flight aerodynamics.
- Reversed flight may have independently evolved in multiple bird lineages.
So next time you see a nimble, backwards-flying hummingbird, take a moment to appreciate the wonder of nature’s aerial engineering!
