[♪ INTRO] 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. And you’ll probably get a kick out of a
lot of our episodes, so why not just click on that subscribe button! Thanks Patreon patrons! Bye! Have a really nice day! I hope that you get, like a, just a surprise
chocolate bar. [♪ INTRO]
