The need for speed


Text and photographs Nicolette Forbes

Speed fundamentals

Impressive and useful in situations where you are chasing or being chased – the ultimate arms race. Having recently had the pleasure of visiting Mala Mala, courtesy of our son who is the operations manager at the resort, we were able to watch wild dogs in action as they pursued impala. The antelope bounded, the dogs glided – they appeared to flow over the quite long grass at a quite bewildering speed.

Wild dogs move so fast they cause panic amongst elephants

It was late in the afternoon and light was fading so we did not see the outcome of the chase. What we did learn was that its possible if they are around to use elephants to locate wild dogs. Elephants apparently can be disturbed by fast moving objects and react by trumpeting and occasionally chasing – which would have explained the reaction to a fast moving delivery truck we heard and saw a few days earlier in Kruger.

Elephants don’t like anything moving too fast around them

It’s generally easy to recognise terrestrial fast movers – the four legged variety are typically fairly large, light bodied with proportionately slender legs and, in the case of cheetahs, remarkably supple spinal columns which allow them to extend their strides. There is no point in being really big and also trying to be a fast runner. In fact it becomes unnecessary if you outgrow any potential predators. There is however, another reason – as an animal grows, its volume (and mass) increase in cubes while the strength in its legs, which support the body, is proportional to the cross sectional area which increases in squares. Consequently the legs must get proportionately bigger on a large animal to support the body mass. So what? It’s a lot easier to move a slender leg faster than a great big one so don’t expect to see an elephant or rhino competing with a tsessebe. That does not mean it is possible for us to outrun a charging elephant!

Somebody might raise the issue that predators such as lions and leopards do not have these speed suiting legs so how do they manage to deal with fast moving prey? Again – a relatively easy answer – lions cooperate and leopards are sneaky with speeds matching their prey over short distances. They can’t do the really slender legs trick because they need their clawed feet, particularly the fore feet, to catch their prey and for this they need to be able to rotate their forepaws much as we can twist our own two fore-arm bones, radius and ulna for the anatomically minded, relative to our elbows and consequently rotate our hands.

How does all this translate in birds?

Birds, the enchanting aviators of the animal kingdom, have fascinated humans for centuries with their ability to navigate the skies with grace and speed. The realm of avian speed is a captivating subject, exploring the intricate interplay of anatomy, physiology, and evolutionary adaptations that allow these winged wonders to break the barriers of the atmosphere. In this article, we will delve into the mechanisms behind the incredible speeds achieved by birds and some of the fastest avian speedsters on the planet.

Lanner falcon landing showing the streamlined shape

Evolutionary adaptations

Over millions of years, birds have evolved specific adaptations to maximise their speed, tailored to their ecological niches and lifestyles. For example, falcons, renowned for their incredible speed during hunting dives, have specialised aerodynamic features such as pointed wings and streamlined bodies. These adaptations minimise air resistance and enable them to reach astonishing speeds, often exceeding 320 km per hour during a dive.

A falcon on the hunt with pointed wings and incredible speed

The anatomy of speed

A bird’s ability to achieve remarkable speeds is intricately tied to its anatomy. Feathered flight, a unique feature of birds, plays a pivotal role in their swift movements through the air. The arrangement and structure of feathers contribute significantly to reducing drag and increasing aerodynamic efficiency. Streamlined bodies and powerful wings further enhance their ability to cut through the air with minimal resistance.

The streamlined shape and long wings of a tern

Muscle power and metabolism

The engine behind a bird’s speedy flight lies in its powerful muscles and efficient metabolism. Birds possess highly developed breast muscles, particularly the pectoralis major, responsible for the downstroke during flight. The rapid contraction and relaxation of these muscles generate the force required for propulsion.

Jackal Buzzard with outstretched wings indicating the important primary feathers and long wings which provide lift and obvious and strong powerful powerful chest muscles which power them

Additionally, birds exhibit a unique respiratory system that enables a continuous supply of oxygen to their muscles during flight. This efficient respiratory system, coupled with a high metabolic rate, allows birds to sustain the energy demands of high-speed flight. A variety of other falcons, swifts and ducks regularly exceed 100 km/hr and one can logically query what sort of energy is required to fly? Flight is energetically expensive which immediately provides an argument for not disturbing roosting or resting birds. It also appears that it is not necessarily a disaster for a bird to lose its ability to fly, providing of course that it does not need to fly to obtain food and there are no predators around. Historically we had the dodo of Mauritius and we still have the flightless penguins of the south, cormorants of the Galapagos and the steamer ducks of South America.

Fastest flying birds in the world

So how fast are birds generally? Having pointed out that flight is energetically expensive it makes sense for a bird to fly as little as necessary, depending obviously on how it obtains its food. A problem here of course is that it is not all that easy to measure flight speeds so the available figures are not always that accurate. Hovering, as perfected by humming birds, is highly expensive but possible because they are very small and have an energy rich diet. It would be difficult to picture a hovering vulture. Birds such as swifts that spend much, or virtually all their time on the wing, apparently do not fly all that fast for much of the time which would fit with a fuel economy strategy combined with their streamlined shape. One cannot but still marvel that at the speed we see in swifts and swallows they can visually detect tiny insects and make the flight adjustments necessary to catch their prey.

So what sort of speedy birds are out there?

Peregrine Falcon (Falco peregrinus): The undisputed king of avian speed, the Peregrine Falcon holds the title for the fastest bird in level flight. With a top speed of around 390 km per hour, these raptors are true aerial acrobats, relying on their sleek bodies and powerful wings to achieve unmatched velocities. The Peregrine cruises in level flight at about 110 km/hr increasing to about 390 km/hr when diving on to prey which it does with largely folded wings. Whether it hits its prey at that sort of speed appears to be moot because one would think that hitting anything at that speed could be traumatic for both parties.

Common Swift (Apus apus): While not as fast as the peregrine falcon, the common swift deserves recognition for its remarkable feats of endurance and speed. These birds can maintain speeds of over 110 km per hour for extended periods, covering vast distances during their annual migrations.

Common Swift – real aerial speed acrobats

Land speed records

So far we have not made any mention of bird runners. Here we have a situation a bit different from the mammals in that there is not the same sort of trend from small, relatively slow species to larger, faster types such as the antelopes, bearing in mind that really large size sets a limit to this trend. Speed on land reflects contact with the ground. The less time feet, toes, paws or hooves spend on the ground the greater the benefit to the runner’s speed. Ground contact is time lost so the more time spent in the air the greater the benefit. Ground runners do not reach the sort of speeds where streamlining is significant although not to forget that human sprint race records have maximum allowable tail winds. To ensure fairness and consistency in recording sprint records, there are guidelines regarding the wind conditions during a race. A tailwind can aid sprinters by pushing them forward and potentially contributing to faster times. However, to maintain a balance and prevent unfair advantages, there is a limit to the allowable tailwind for a race result to be considered an official record.

Streamlining becomes significant when resistance to the speed of movement starts becoming a factor. This occurs at fairly low speeds in water where its density rapidly drives the very obvious streamlining in the body shapes of seals, dolphins, marlin, tunny and the shape taken up by an octopus when it makes an escape. All birds are streamlined to some degree, courtesy of their feathers. Anyone who seen a featherless bird would agree that without feathers it is about as streamlined as a brick. What streamlining does, whether in water or air, is to allow an object to move through either medium without generating turbulence which would be equivalent to a resistance to movement.

In the African context the fastest running bird is certainly the Ostrich with its long legs and two-toed feet.

Ostrich foot showing the powerful modified feet adapted for speed with two toes

It is actually the fastest running bird in the world.

An Ostrich in full stride – the fastest bird runners in the world

Their feet act like springs, providing cushioning and shock absorption as they propel forward. The ostrich’s speed and anatomy is so unique that scientists have even designed mechanical robot feet inspired by this bird. At the other size end of the running bird spectrum is our Helmeted Guineafowl which can match a galloping horse (from personal experience).

Analogs are found globally too. In Australia where we have an ostrich equivalent in their emus, South America has its rheas while North America has its Roadrunner – a speedy type of cuckoo of cartoon fame – which according to the National Geographic bird guide does not despite popular belief go “beep beep”. This should make sense to anybody familiar with the Wile E. Coyote of Looney Tunes fame.

History of the study of speed

The study of speed in birds unveils the marvels of avian flight and the complex adaptations that have evolved over aeons. From the streamlined bodies of falcons to the endurance of swifts, each species showcases a unique approach to achieving optimal speed in the skies. As our understanding of bird physiology and aerodynamics advances, so too does our appreciation for the breath-taking speed and agility displayed by these feathered miracles of flight.

A Cape Vulture showing off its powerful wings

The whole story of the interactions of bird speeds, wing shapes, lift, drag and a plethora of other terms and factors can start to make sense when checking what happens with fixed wing aeroplanes; when dealing with birds where the wing provides lift and propulsion and in any species can change shape, be prepared for a marathon, going back – believe it or not – to Leonardo da Vinci. Leonardo da Vinci, the polymath of the Renaissance, was fascinated by the study of motion and speed. His approach to studying speed was rooted in both artistic and scientific inquiry. Leonardo’s studies on speed were part of his broader investigations into anatomy, engineering, and the natural world. Birds, with their mastery of flight, particularly intrigued Leonardo. He made detailed studies of birds in flight, carefully noting the positions of their wings and bodies. His observations of birds in motion contributed to his understanding of aerodynamics and the principles of lift, which are essential for understanding the speed and efficiency of flight. Leonardo da Vinci’s method of studying speed was a holistic approach that combined artistic intuition with scientific curiosity. His ability to merge artistic creativity with scientific inquiry allowed him to explore the intricacies of motion and speed in a way that laid the foundation for future advancements in anatomy, physics, and engineering.

Author photo: Pat McKrill

About the author

Nicolette Forbes was born in Durban and is passionate about all things KZN and its environments. With an interest in all things living from a young age it was no surprise that her chosen career path ended with her becoming a professional biologist having studied biological sciences at the University of Natal, Durban (now University of KwaZulu-Natal). Studying was followed by a lecturing stint to both biology and medical students for nine years before leaving the university to put her knowledge into practice with an ecological consultancy specialising in coastal habitat assessments.

Birding has been a passion from her high school days and birdwatching, atlassing. photography and being in the bush are her favourite things. Currently the Chair of BirdLife eThekwini KZN, the club covering the Greater Durban area, Nicolette has also through the non-profit EcoInfo Africa, partnered with Kloof Conservancy to run environmental courses focussed on birds.