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  • 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 reallythis 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.

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B1 中級

7個改變你對鳥類印象的巢穴 (7 Nests That Will Change How You Think of Birds)

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    林宜悉 發佈於 2021 年 01 月 14 日
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