The Magic of Buoyancy: How Do Ducks Float?
In 1992, a cargo ship accidentally released thousands of rubber duckies into the Pacific Ocean. Amazingly, many of these yellow duckies are still out there floating bravely and ending up on coastlines worldwide. These toys have remained afloat for over twenty years because they are light and air-filled. Moreover, seawater is dense enough to hold them. But how do real-life ducks float? The biomechanics of this phenomenon makes ducks unique birds.
In a nutshell, ducks float because of their natural buoyancy, meaning they are lighter than the water they displace. This might seem confusing but read on to understand how ducks float and their other behaviors in the water.
The Science of Duck Floating
Before you understand how ducks float, you should understand what floating means. Floating above water with no external effort is called buoyancy. Archimedes’s principle, also called the physical law of buoyancy, states that when a body is submerged in a fluid at rest, an upward force equivalent to the weight of the fluid its body displaces moves it upward.
Thus, for a body to remain buoyant, it should weigh less than the fluid it displaces. Ducks have several characteristics that keep them relatively light to stay buoyant. Here are these characteristics:
- Hollow bones, unlike human bones full of bone marrow. You might assume that this means the bones are also lighter than those of other animals. However, a duck’s hollow bones have dense outer walls to keep them from fracturing, so they are not light.
- Bodily air sacs, in addition to lungs, make up a complicated avian respiratory system. The air sacs help birds fly, with floating being their secondary benefit. These air sacs spread throughout a duck’s body, allowing an uninterrupted oxygen flow that makes the bird lighter than the water it displaces.
- Water-repellent feathers that are covered with oil from the uropygial gland at the tail’s base. Since water and oil do not mix, the duck’s feathers cannot absorb water and become waterlogged to make the bird heavy and sink. In so doing, the oiled feathers contribute to the lightness that will make a duck float.
- Interlocking feathers that trap air. The blank air spaces between these feathers, known as contour or pennaceous feathers, overlapping or lying on top of each other keep ducks light and allow the exertion of little buoyant force on the water to keep the bird afloat.
How Ducks Control Their Buoyancy
Ducks cannot sink but sometimes dive underwater to escape predators or look for food. To control buoyancy, they keep preening their feathers to retain their waterproof nature so that they do not become waterlogged and make the duck heavy. Some inspirational quotes allude to ducks paddling underwater to remain afloat.
This is factually incorrect because ducks do not paddle to remain buoyant. They can even relax then fall asleep in the water without sinking. The only times ducks paddle are when fighting a current or steering. In fact, ducks can remain afloat for life, provided the water is warm enough, and they have food.
How Ducks Move In the Water
A duck’s feet help it move in water and on land. The feet are primarily designed for paddling as they are set back on a duck’s body. This position and their webbing give ducks their distinct waddle when walking. When in water, the duck will push downward and backward with its feet and legs.
The bird creates more surface area and pushes more water when moving by spreading out its toes’ webbing on the down stroke. The toes are turned inward or folded together during the forward stroke to reduce water resistance. These motions give ducks the thrust and lift they need to propel themselves through the water.
How Ducks Keep Themselves Dry
If you watch ducks for some time, you will notice them using their beaks to nib their feathers. The practice is known as preening, where the bird spreads oil on its feathers’ top layer. This oil comes from a gland near its tail and makes its feathers waterproof since water cannot get past oil. The oiled feathers act as a natural raincoat for the duck.
A duck’s feathers interlock to trap air which will keep the bird waterproof since water cannot stick to air. The air spaces also keep the duck warm by trapping air between the body and wings. Beneath the oiled and interlocked contour feathers are soft feathers called down feathers that keep the duck warm. These cannot repel water, so ducklings covered in natal down are kept in the nest to protect them from hypothermia if they become wet.
Can Ducklings Float In Water?
Just because a duck can float does not mean you should toss a duckling in water, expecting it to be happy. Ducklings have air sacs and hollow bones that make them buoyant, but the uropygial glands for making feathers oily only become fully functional at 4-8 weeks old.
After hatching, mother ducks use their glands to oil their young ones and protect them from water when outdoors. When hatched in an incubator, the ducklings have to wait until they are 4-8 weeks old to oil their feathers.
It is best to always supervise ducklings around water and only allow them around warm water that is shallow enough for them to stand on the bottom. When they come from the water, always keep them warm.
These reasons might make you think you should keep your ducklings out of the water until they are at least a month old. However, experts agree that when you expose a duckling to water early, it learns how to preen early.
Though ducks are exceptional all-around, one of their outstanding characteristics is their ability to float almost effortlessly. This is possible because of the birds’ hollow bones, water-repellent feathers, bodily air sacs, and interlocking feathers. The ducks maintain their buoyancy by keeping their feathers oiled and thus water-repellent.
They move in water using their legs and feet and keep themselves dry by preening. Ducklings can float in water when they turn 4-8 weeks old, and their uropygial glands mature.