Speed of Flight
How can birds fly faster than cars on the highway while in level flight? With recorded speeds of over 33.5 meters per second (75 mph), some birds fly faster than people drive. But how do birds fly and what lets them go so fast? This article will explore some of the many answers to this question.
The first part of the question is: what makes birds fly? They have many challenges such as gravity, air resistance (Mattson, 2022), long periods of flight (H. Large, 2024), and a need to change direction. These all limit a bird's flight capabilities.
There are four forces applying to birds in flight: gravity, lift, thrust, and drag. Gravity and lift are opposite forces. Gravity is the force that pulls down birds proportionally to their weight, while lift is the force generated by the birds that pushes them upwards. Additionally, thrust and drag are also opposing forces, thrust being the force of their forward motion or their speed, and drag being the friction force applied by air particles when flying and what slows them down. When lift and thrust are greater than gravity and drag respectively, the bird can fly (Mattson, 2022). To fly, birds use their environment, such as using pockets of hot air, called updrafts, which birds can utilize to easily move upwards or soar because the air is moving upwards (Lindholm, Bodette, 2023).
A bird has many body parts that assist its flight. To keep level, a bird must keep their center of gravity in the middle of its wings, beak, and tail. To do this, birds have many adaptations that have slowly perfected their dobies for flight. For example, they do not have a nose or teeth because those would be too heavy on their beak and make them tip forward. They also have very short and hollow bones to limit the weight (Journey North, 2019). Additionally, their elongated body gives them less resistance from the air. In fact, a bird’s entire body is made to be as light as possible so that it has less gravity pulling it down (BBC WM, 2024).
The biggest contributing factor to bird flight is a bird’s wings. Different shapes and sizes of wings allow birds to fly in different ways. For example, the pointed wings of ducks allow them to fly at extremely high speeds, while the much larger wings of eagles’ allow them to soar and conserve their energy (BBC WM, 2024). Bigger wings create lift more easily, allowing for the bird to meanuver easier. Birds with smaller wings must travel much faster to achieve that lift. This means that the smaller a bird's wings are, the faster it is required to fly.
Birds make two different motions when flapping their wings: the upstroke and downstroke. The downstroke propels the bird, creating lift and thrust, adding to their forward momentum, or in other words, increasing the bird’s speed. To gain lift, the cross-section of bird wings are shaped like a comma (Science Learning Hub, 2011). There is then less surface area on the top of the wing, and because of this, the wind moves faster over the top than the bottom (Mattson, 2022). This creates a difference in pressure above and below the bird, giving them lift that allows the bird to stay in the air. The upstroke involves folding their wings so that they can reset with the least amount of air resistance (Science Learning Hub, 2011). This is called Bernoulli's principle and it is one of the important principals for lift, and allows for gliding. However, there are other important forces also at work, as can be seen when planes fly upside down, because if Bernoulli’s principle was the largest force acting upon it, it would move down. However, certain planes are capable of sustained flight upside down even though their wings are built to fly right side up.
So what makes birds go so fast? The first factor is how the bird’s wings are shaped. As previously mentioned, different kinds of wings can change a bird's speed, with long, pointed wings being the fastest. This is because the point helps reduce the drag while the big size helps to increase thier thrust (Rovatti, 2023). The second factor is the weight of the bird. Birds are designed to never carry excess weight. One way they do this is by dumping their feces immediately. A third reason is that they
Interestingly, scientists have found that birds fly faster in larger flocks. There are a few theories on why this happens. One is that all the birds fly at the speed of the fastest ones, and more birds mean faster top speeds. The other is that flying in formation creates turbulence, meaning that birds take less energy to go the same speed when flying in the back (Lund University, 2016). With more birds in a flock, they can all rotate positions only spend short amounts of time in the lead while the rest can rest more. Birds also use turbulence to accelerate when not in flocks. Because turbulence is a commonly occurring phenomenon that can happen in many ways, birds will use it to take a moment to rest or to speed up (Nutt, 2021). Some kinds of turbulence they use are mechanical turbulance, thermal turbulance, frontal turbulance, and wind shear. Mechanical turbulence is when there are things blocking the airflow such as buildings or mountains, making the air go in different directions. Thermal turbulence is when the sun unevenly heats the surface causing the air to go up in some places much faster, creating updrafts and downdrafts. Frontal turbulence is when hot and cold fronts collide, such as during thunderstorms. This creates irregular circulation on their border. Wind shear is when there is a lot a rapid changes is the wind, in speed or direction. Birds will then adjust their flight to work with the turbulence so that they can be as efficient as possible (National Weather Service, 2019).
Many things affect how fast birds fly. Every part of their bodies is adapted to meet their needs and allow them to travel further. The fastest birds can go at incredible speeds by combining the power to generate a lot of thrust with optimized wings and a lightweight body. Birds that take all the most important qualities of fast flight, such as the common swift or racing pigeons, are able to achieve some of the highest speeds.
References
Mattson, C. (2022, September 19). The Physics of Flight. Schlitz Audubon. https://www.schlitzaudubon.org/2022/09/19/the-physics-of-flight/
How do birds fly? (n.d.). Vermont Public. https://www.vermontpublic.org/podcast/but-why-a-podcast-for-curious-kids/2023-09-08/how-do-birds-fly
How Birds Fly: An In-Depth Journey North Lesson. (2019). Journeynorth.org. https://journeynorth.org/tm/FlightLesson.html
How Do Birds Fly? (n.d.) Www.discoverwildlife.com. https://www.discoverwildlife.com/animal-facts/birds/how-do-birds-fly
How birds fly. (2011, September 21). Science Learning Hub; Science Learning Hub. https://www.sciencelearn.org.nz/resources/303-how-birds-fly
An unnecessarily drawn-out analysis of bird flight for animation. (2023, January 1). Animator Notebook. https://www.animatornotebook.com/learn/bird-flight
Lund University. (2016, August 16). Birds fly faster in large flocks. Phys.org. https://phys.org/news/2016-08-birds-faster-large-flocks.html
Large, H. (2024, March 26). What’s The Longest Time A Bird Can Fly Without Landing? IFLScience. https://www.iflscience.com/whats-the-longest-time-a-bird-can-fly-without-landing-73534
Pigeon racing | sport. (n.d.). Encyclopedia Britannica. https://www.britannica.com/sports/pigeon-racing
Nutt, D., & University, C. (n.d.). More than a bumpy ride: Turbulence offers boost to birds. Phys.org. https://phys.org/news/2021-06-bumpy-turbulence-boost-birds.html
National Weather Service. (2019). Turbulence. Weather.gov. https://www.weather.gov/source/zhu/ZHU_Training_Page/turbulence_stuff/turbulence/turbulence.htm
Nutt, D., & University, C. (n.d.). More than a bumpy ride: Turbulence offers boost to birds. Phys.org. https://phys.org/news/2021-06-bumpy-turbulence-boost-birds.html
National Weather Service. (2019). Turbulence. Weather.gov. https://www.weather.gov/source/zhu/ZHU_Training_Page/turbulence_stuff/turbulence/turbulence.htm