How Do Ducks Float?

Ducks can hold extra air in their feathers and bodies, making it easy for them to float -- and to squeeze out the air and dive when they want to. Learn more about ducks and bouyancy in this episode of BrainStuff, based on this article: https://animals.howstuffworks.com/birds/duck-float.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff.
Lauren vogelbam here on January twenty ninth of nineteen ninety two,
A cargo ships build a portion of its contents into
the Pacific Ocean, thus releasing some twenty eight thousand little
yellow rubber ducks and other bathtub toys to journey around

(00:24):
the globe. Beachcombers and other amateur and professional ocean enthusiasts
logged findings of them for at least twenty years. The
last report I know of is from August of twenty thirteen.
They've ridden ocean currents up the eastern coast of the
United States, along the shores of Greenland, and through the
ice pack in the Arctic Ocean. Some two thousand are

(00:47):
still unaccounted for. How these simple bathtub toys remained afloat
for so long isn't much of a mystery. After all,
they're made of lightweight rubber and filled with air. It's
no wonder the dense sea water holds them up. But
how do their flesh and blood brethren accomplish the same task.
Real ducks aren't made of plastic, and they contain more

(01:09):
than just air. Today, let's talk about how ducks float.
To understand this, you first have to understand why anything floats.
Objects either float or sink in water because of what's
called buoyancy. When an object placed in water weighs less
than the amount of water that it displaces, the object floats.

(01:31):
If it weighs more, the object sinks. If that cargo
ship had been transporting bowling balls, you can bet they
wouldn't be cruising the high seas. Rubber ducks, however, are
a different story. They typically weigh no more than say,
zero point two ounces, but they take up about four
point five cubic inches of space. For our metric friends,

(01:54):
that's about five grams and seventy five cubic centimeters. So
that means that the water that they displace weighs over
two and a half ounces or seventy five grams, so
that water significantly outweighs them. Therefore, the heavier sea water
will keep them afloat. Real ducks are also lighter than

(02:16):
the water they displace, but it takes several things working
in tandem to achieve that lightness. First up, ducks have
a special gland called the europhygeal gland, or the prene gland.
This gland, located at the base of their tail, produces
an oil that the ducks spread over their bodies to
make their feathers water repellent. If you've ever seen ducks

(02:40):
preening themselves and seeming to pay special attention to their
tail feathers, that's why they keep going back to that
gland for more oil. Because the oil treated feathers resist
getting saturated with water, the birds weigh less than they
would if their feathers absorbed that water. This is also
how the phrase like water off a duck came about.

(03:02):
In addition to their water proofing abilities, duck feathers possess
another quality that helps them to float. They trap air.
The bird's feathers are tightly interlocked with a system of
bendy barbs that hold air in. You know those little
wings that kids wear on their arms in the pool
to help them swim. Ducks practically have those built into

(03:23):
their feathers. If they need to dive under water for
a quick snack, they just squeeze the air out by
pressing their feathers in. The feathers will trap air again
soon after the duck resurfaces and shakes any beads of
water off of its oil treated feathers. Ducks further have
a system of internal air sacks that helps to keep

(03:44):
them buoyant. These sects, which include the duck's lungs and
are located along the length of the duck's body, are
the equivalent of having miniature helium balloons inside of them.
The secs stay filled with air unless the duck wants
to dive underwater, at which point it squeezes the air out. However,
one feature that does not help ducks float is the

(04:07):
weight of their hollow bones. Most birds that fly and
some that don't, and some dinosaurs have a bone structure
that's webbed through with pockets on the inside instead of
being relatively solid, which most human bones are. If you
think of it in terms of candy, the cross section
of hollow bird bones is sort of like honeycombed toffee,

(04:30):
and many human bones are more like a chocolate bar
with a few crunchies in it and some kind of
chewy center, sort of. People used to think that the
air pockets in birds hollow bones made them lighter, but
it turns out that it doesn't because of that webbed
or honeycomb structure. Birds bones are actually more dense than

(04:52):
mammal bones. They have to be because they have to
be stiffer and stronger so that they don't break the
real benefit of these hollow bones is that they're essentially
part of the bird's lung system. Air sacks from a
bird's lungs form and attached to the hollows in its
bones as the bird grows, so when the bird flies,
it has extra space to take in oxygen. That means

(05:16):
extra oxygen will find its way into the bird's blood,
which will give it extra energy for flight. I guess
it's possible that when a bird with lots of hollow
bones really breeds in it might give them an edge
in floating, but it would only be for as long
as the breath lasts, so not really useful overall, and

(05:36):
ducks don't have that many hollow bones to begin with.
Not all birds have the same number. Birds that spend
a lot of time gliding or soaring have more, and
birds like ducks that spend a lot of time diving
have fewer. Some diving birds like penguins, puffins, and loons,
don't have any hollow bones at all, which indeed places

(05:57):
them at odds with the rubber duckies that we discussed early,
which are entirely hollow, by the way, if you would
like to learn more about their journey. There's been a
bunch of research published about these rubber ducks and what
they mean for our oceans and the plastics that wind
up there. This includes at least two books. A one

(06:17):
is called This Is a Long One Moby Duck, The
True story of twenty eight eight hundred bath Toys lost
at sea and of the Beachcomber's oceanographers, environmentalists and fools,
including the author who went in search of them, and
another called slightly more simply Flotsymmetrics and the Floating World.

(06:38):
How one man's obsession with runaway sneakers and rubber ducks
revolutionized ocean science. Today's episode is based on the article
how do Ducks Float? On HowStuffWorks dot Com written by
Jennifer Horton. Brain Stuff is production of by Heart Radio
in partnership with how Stuffworks dot Com and is produced

(06:59):
by Tyler Klais. Four more podcasts my Heart Radio, visit
the iHeartRadio app, Apple Podcasts, or wherever you listen to
your favorite shows.