When you think about a birds' nest, you're probably imagining, like,

some twigs stuck together on a branch of a tree.

And that is definitely a type of bird's nest.

It turns out, though, that there are a lot of different nests out there,

with a wide variety of shapes and sizes.

They don't need to be in trees. They don't even need to be made out of sticks.

And there's no single reason for why birds' nests are so different.

Nests are places where birds can lay eggs and raise their young,

and the advantages of building one type over another can include avoiding predators,

creating a better climate for survival, or finding a mate.

Today, we're going to explore the incredible diversity of these structures

by looking at 7 differently impressive nests.

As the title says, we're gonna change the way you're thinking about birds.

Because, who wants to keep thinking about birds the same way all the time?

Bald eagles are probably best known as the national symbol of the US,

but they can be found all over North America.

Their nests are like the supersized version of what you probably imagined earlier;

that is, a nest of sticks on top of a tree.

Nests in trees have certain advantages over nests on the ground:

they can provide additional safety against predators

and be more available than other potential spots.

And it turns out that competition over some types of homes, like tree holes,

can get pretty intense since they're already really sturdy.

So building a nest means less competition.

One reason the nests of bald eagles are so humongous

is because the birds themselves are just big.

Bald eagles are typically around a meter long, with a wingspan more than twice that size.

And a nest needs to be able to accommodate both parents as well as their quickly growing kids.

Eagles also continue to improve the same nest year after year,

possibly as part of their courtship behavior, so the nests can grow larger over time.

In fact, a pair of bald eagles in Florida in 1963 set the world record for the largest birds' nest.

It clocked in at 3 meters wide and 6 meters deep.

So for context, that means you could've dropped an entire giraffe inside it!

Don't put giraffes inside bird's nests!

It's a really… this is just for mental exercise.

To build such large nests, the male and female work together for months.

They often locate these nests on the top of the tallest tree in the area,

which gives them a good vantage point over their territory.

The pair stack and weave together branches,

lining the inside with soft materials like grass, moss, and feathers.

And the result is a strong, sturdy nest that they can return to

year after year, or even decade after decade.

Nests have been known to be used for as long as 35 years.

The common tailorbird of Asia takes the nest weaving process one step further

by literally sewing its nest together like, a tailor.

It's the female that does the sewing, although the male sometimes helps out by

collecting materials or lining the nest with soft things like feathers and plant down.

To make the nest, the female uses her beak

to place leaves together and poke holes around their edges.

Then, she threads spider silk, plant fibers,

or even stolen string through the holes to form stitches, which can number up to 200 per nest.

The entire process takes several days,

but the end result is a leafy pouch that blends in well with the surrounding foliage.

This camouflage is especially effective because the bird takes care in aligning the nest,

exposing only the top surfaces of the leaves

so that everything matches the orientation and color of nearby plants.

And because the holes the tailorbird puts in the leaves are tiny,

the leaves rarely turn brown, making it even harder to spot when everything else is green.

All of this helps conceal the tailorbirds' nest and protect it from predators.

A final touch is that the nest actually hangs from the tree rather than sitting directly on it.

This is common for nests in hot countries,

and it helps protect the birds' eggs from being eaten by monkeys and snakes.

The brushturkey of eastern Australia takes the opposite tactic

by building their nest right there on the ground.

And those nests are essentially giant compost piles

that the birds can use to incubate, or warm, their eggs until they hatch.

This so-called mound is also seen in most other members of the birds' family, the megapodes.

Now, many modern-day birds, of course, sit on their eggs to keep them warm.

So it's unclear why brushturkeys and their relatives don't.

Mound-making could have emerged as an alternative nesting strategy

after changes in climate that happened hundreds of millions of years ago.

Or it could have been an ancestral feature that megapodes somehow retained:

having an external heat source is common in reptile nests.

Whatever the case, the mound is built by the male brushturkey.

During winter, the bird collects forest vegetation

like leaves, moss, and branches, then mixes them together.

As the pile decomposes, it generates the heat needed to incubate the eggs.

But, if the temperature is too hot, male embryos are less likely to make it.

And if it's too cold, female ones don't fare as well.

So the wrong temperature can tip the gender balance of the young.

To prevent this, the brushturkey checks the temperature of his mound with his beak

and adds or removes vegetation as necessary.

It's a very precise process, since adding about 1 centimeter of material

can increase a mound's temperature by about one and a half degrees Celsius.

The size of the mound also plays an essential role in keeping the temperature steady:

adding more material reduces the amount of heat the mound loses,

so a bigger mound better insulates the eggs from the outside environment.

The end result is something the size of a car.

So building this nest is a lot of work.

But it's worth the effort, because if the male does well, he can attract a lot of mates.

Several different females will lay their eggs in one good quality mound,

while lower quality ones may not attract any females at all.

Another enclosed nest comes from the hamerkop of Africa,

who build domes of mud, grass, and as many as 10,000 sticks.

To create that nest, both the male and the female work together,

building up a central, cup-like core first before adding to the sides.

That makes the final nest pretty hard to access,

since most of its structure is covered except for one small tunnel leading to the inside.

They're also really, really big: up to two meters across and two meters tall.

That's three times taller than the bird itself.

In fact, Hamerkop nests are so large that snakes and lizards

have been known to live inside, at the same time the bird is nesting,

which gave the birds the pretty awesome reputation of being mythical, shapeshifting beasts.

That reputation may have been bolstered by the bird's practice of decorating the nest

with brightly colored or otherwise unusual objects like snakeskin or even dead birds.

Scientists are still puzzling over why these features are there.

One idea is that the outside ornaments help the male strut his stuff, but nobody's really sure why.

The nest's large size might help the hamerkop to support a larger number of eggs,

and its enclosed nature presumably protects the eggs and offspring better than an open nest.

After all, the massive structure can support the weight of a human,

and its walls of mud act as both insulation and waterproofing.

The nest of the piping plover is basically the opposite.

These birds nest on the sandy beaches of North America,

where building materials can be in short supply.

So, the plover makes do with what's called a scrape nest,

which is common in open areas with limited resources.

The male bird literally scrapes away sand, gravel,

and other debris to make a small depression on the shore. That's it.

Sometimes, the nests are lined with pebbles, which are chosen to match the color of the eggs.

These help regulate the temperature of the eggs, especially if they're left unattended.

Still, they are about as minimalist as nests can get.

And since these nests are pretty accessible to land predators,

the birds have developed other defense mechanisms to help them survive.

Plovers rely strongly on camouflage to protect themselves from predators.

Plover eggs are light-colored and speckled, helping them blend in with their sandy surroundings.

And being in the open isn't all bad.

Nesting on flat areas rather than in a tree can also help the birds spot approaching predators,

as there is nowhere for them to hide as they get closer.

Rather than in a tree or on the ground, the pied-billed grebes of the Americas build nests that float.

This actually makes a lot of sense because the birds are water-dwellers.

Their legs are set near the back of their body, making them great swimmers

but not very good walkers, so it would be inconvenient for them to have to nest on land.

But while grebe nests have been described as floating platforms,

it's not like they use them to sail the high seas.

They're actually anchored to plants so that they don't drift away.

Building the nest is a joint effort of both the male and female grebe,

who often have to dive to collect dead and decaying plants.

They also may pick up material that's floating on the water's surface.

It all goes into a pile, and sometimes that pile will start to sink.

As that happens, the grebe will tuck additional material underneath the eggs to keep them above water.

This may all sound like they're spending a lot of energy to literally save a sinking ship, but it's worth it.

Like with the brushturkey, all that decaying material can help incubate the egg,

and nesting in the water lets the grebes stay where they're the most comfortable.

Just like the bald eagle, hummingbirds also have a world record:

one member of the family builds the world's smallest birds' nest.

That's the nest of the bee hummingbird in Cuba, which clocks in at a mere

2 centimeters wide and three centimeters deep; about the size of a thimble.

Most hummingbird nests tend to be a little bigger, more like the size of a ping pong ball.

All of this is very adorable.

These small birds all live somewhere in the Western Hemisphere.

But despite that wide geographic range and the fact that

there are over 300 varieties of hummingbird, they all tend to build pretty similar nests.

Of course, not every hummingbird nest is gonna be made out of the same stuff.

There are variations in materials depending on species, geography,

and even individual preference, but the basic blueprint is generally the same.

Hummingbird nests are typically made by the female,

who weaves a cup out of plant material and sticky spider silk,

which helps bind, insulate, and camouflage the structure.

Another advantage of spider silk is that it's soft and stretchy,

allowing the nest to stretch as the young hummingbirds grow.

That's especially important because young hummingbirds

aren't likely to leave the nest until they can fly by themselves.

Other stuff, like discarded feathers, can also help camouflage the nest.

Meanwhile, the inner layer, which helps keep the eggs warm and cozy,

usually contains soft materials like the white hair of a dandelion.

Yes! they use dandelion fuzz.

Cuz it wasn't cute enough already?!

And the 7 nests that we just talked about are just a small sampling

of the many amazing varieties out there.

After all, there are estimated to be over 18,000 different bird species!

And all of them have to put their eggs somewhere.

From teeny, adorable cups to massive compost mounds,

the diversity of birds' nests is a great illustration of

how every species must adapt to its own environment.

Thanks for watching this episode of SciShow!

If you liked learning about these amazing nest-builders,

I think you will love our episode on the birds that lived alongside dinosaurs.

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