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8 Animals That Get Their Color From Food

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Charlie and the Chocolate Factory gives new meaning to “you are what you eat.” In the classic kids’ book, a girl named Violet Beauregarde chews some experimental blueberry-flavored gum—and it turns her blueberry-blue. But for some animals, that’s not too far from the truth: they get their colors from the food they eat. Here are eight critters that get their hues from their diet, plus two honorable mentions: a bird that’s shinier when it eats bugs, and a garden plant that switches between pink and blue.

1. BLUE-FOOTED BOOBIES

Native to warm waters of the eastern Pacific, blue-footed boobies (above) have, well, bright blue feet. They use this fancy footwear to attract mates via an awkward dance. The blue color comes directly from carotenoid pigments in their fishy diet, and healthier birds can afford to expend more pigment to intensify their foot coloration. So, a bird with brighter feet is a more attractive partner. 

2. EASTERN EMERALD ELYSIAS

Karen N. Pelletreau et al. via Wikimedia // CC BY 4.0

Its name is straight out of a fantasy novel, and that’s not even the coolest thing about this marine slug-like animal. The eastern emerald elysia has turned itself, at least in part, into a plant. It’s green, it’s shaped almost exactly like a leaf, and it can do something that animals usually can’t do: make food from the sun.

Plants are green because their cells have special green parts called chloroplasts that make energy from the sun. When the eastern emerald elysia eats some algae, it adds insult to injury by stealing the algae’s chloroplasts. Then it basks in the sunlight and absorbs the food that the chloroplasts make. It’s able to keep these stolen parts functioning for nearly a year—enough time so that it may never need to eat algae again.

3. SALMON

Salmon flesh has such a lovely hue that we call it, well, salmon pink. These fish get their color from the small shellfish they eat. Farmed salmon are fed natural or synthetic pigments so that their meat retains this familiar tint.

4. FLAMINGOS

Everyone knows that flamingos are pink and bluebirds are blue, right? Well, not really: Flamingos are definitely pink, but bluebirds’ blue color is an illusion.

Birds have different ways of looking colorful. A bluebird’s feathers have special structures that break up light and reflect just the blue parts. This makes them look blue—but only when light is hitting them in just the right way. If you take a bluebird feather and shine a light behind it, the feather will appear brown. The same is true of most other blue and green birds, from blue jays to green parrots.

Flamingos, on the other hand, have feathers that stay pink no matter which way you look at them. That’s because they’re full of pink-red pigments called carotenoids—carrots are orange because they contain a type of carotenoid. Flamingos get this pink stuff from the shrimp that they eat. If they don’t consume the right food, they’ll turn grayer. Zookeepers have to feed their flamingos food with the right pigments to keep them rosy.

5. GOLDFINCHES

Many other birds get their hues from carotenoid pigments. That’s true of American goldfinches, which are blazing yellow in breeding season. Female goldfinches size up males based on the vibrancy of their yellow: Brighter males are healthier and have better diets, so they’re more attractive.

6. CEDAR WAXWINGS

Cedar waxwings are small, sleek songbirds. Their tails usually have yellow tips—but some have red tails, and it’s all our fault.

Cedar waxwings are native to North America, and they love eating berries. A few decades ago, people brought Asian honeysuckle varieties to North America. These plants spread throughout the forests, and they produce big red berries that are impossible for a hungry waxwing to resist. The berries are rich in a reddish pigment that builds up in waxwing tails, turning them from yellow to orange.

7. NUDIBRANCHS

Related to snails, nudibranchs live in the ocean, and they’re mind-blowingly colorful. Really: feast your eyes on these hues. They’re so colorful, in fact, that there’s a blog matching different species to David Bowie’s outfits.

Many nudibranchs get their bright colors from their prey. One species, the red sponge dorid, is bright red and probably gets its pigment from the red sponges it eats. This has the added benefit of giving the red sponge dorid some amazing camouflage when it’s crawling on its spongy food.

8. FRILLED DRAGONS

Remember that scene in Jurassic Park when a neck-frilled dinosaur terrifies the hapless hacker Dennis Nedry, then spits poison on him? The movie’s creators got their inspiration from Australia and New Guinea’s frilled dragons—also known as frill-necked lizards. These remarkable reptiles flare their huge frills when they’re scared, or as part of territorial or courtship displays.

Frilled dragons’ frills come in different colors, from red to orange to yellow. The colors depend on their geographical location—and the variation is probably because of the different amounts of pigment in their prey.

HONORABLE MENTION #1: HUMMINGBIRDS.

Many hummingbirds have shiny, iridescent patches of feathers. These hues don’t come from their diet; they’re the result of specially structured feathers that reflect light in amazing ways. But even though hummingbirds don’t get their color directly from their food, their diet has a strong influence on how shiny and bright they’ll be. 

Anna’s hummingbirds are tiny, fast-moving birds that live along the Pacific Coast of North America. Their foreheads and chins are iridescent red-purple. When they’re staking out territory, they stick up these feathers and enthusiastically show them off. To keep up their high-energy lifestyles, these birds eat sugary flower nectar. But there’s one problem with this sweet diet: Hummingbirds need protein to make their shiny feathers, and there’s not a lot of protein in nectar. Another option is to catch and eat insects, but this takes a LOT of energy. Scientists have found that Anna’s hummingbirds on higher-protein diets have shinier, redder crowns.

HONORABLE MENTION #2: HYDRANGEAS

Plants can also change color depending on their diets. Hydrangeas are familiar garden flowers, and they’re like living mood rings. If a hydrangea plant is absorbing aluminum from the soil, it turns bubblegum pink. In the absence of aluminum, it’s cotton candy blue. Gardeners adjust the colors by tweaking the soil pH—acidic soil promotes blue colors and basic promotes pinks.

All photos courtesy iStock unless otherwise noted.

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14 Bold Facts About Bald Eagles
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Bald eagles are powerful symbols of America—but there’s a whole lot more to these quirky birds.

1. YOUNG BALD EAGLES AREN'T BALD.

A young bald eagle with a brown head on a beach.
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So obviously adult bald eagles aren't really bald, either—their heads have bright white plumage that contrasts with their dark body feathers, giving them a "bald" look. But young bald eagles have mostly brown heads. In fact, for the first four or five years of their lives, they move through a complicated series of different plumage patterns; in their second year, for instance, they have white bellies.

2. BALD EAGLES SOUND SO SILLY THAT HOLLYWOOD DUBS OVER THEIR VOICES.

A red-tailed hawk.
A red-tailed hawk's screech is usually dubbed over the bald eagle's weaker scream.
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It's a scene you’ve probably seen countless times in movies and on TV: An eagle flies overhead and emits a rough, piercing scream. It's a classic symbol of wilderness and adventure. The only problem? Bald eagles don't make that sound.

Instead, they emit a sort of high-pitched giggle or a weak scream. These noises are so unimpressive that Hollywood sound editors often dub over bald eagle calls with far more impressive sounds: the piercing, earthy screams of a smaller bird, the red-tailed hawk. If you were a fan of The Colbert Report, you might remember the show's iconic CGI eagle from the opener—it, too, is making that red-tailed hawk cry. Listen for yourself and decide who sounds more impressive.

3. THEY EAT TRASH AND STOLEN FOOD.

Two bald eagles guard their prey against two magpies on a snowy field.
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Picture a majestic bald eagle swooping low over a lake and catching a fish in its powerful claws. Yes, bald eagles eat a lot of fish—but they don't always catch them themselves. They've perfected the art of stealing fish from other birds such as ospreys, chasing them down until they drop their prey.

Bald eagles will also snack on gulls, ducks, rabbits, crabs, amphibians, and more. They'll scavenge in dumpsters, feed on waste from fish processing plants, and even gorge on carrion (dead, decaying animals).

4. BALD EAGLES USUALLY MATE FOR LIFE ...

Two bald eagles perched on a tree.
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Trash and carrion aside, they're pretty romantic animals. Bald eagles tend to pair up for life, and they share parenting duties: The male and the female take turns incubating the eggs, and they both feed their young.

5. … AND THEY LIVE PRETTY LONG LIVES.

Two bald eagles sitting on a rock.
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Those romantic partnerships are even more impressive because bald eagles can survive for decades. In 2015, a wild eagle in Henrietta, New York, died at the record age of 38. Considering that these birds pair up at 4 or 5 years of age, that's a lot of Valentine's Days.

6. THEY HOLD THE RECORD FOR THE LARGEST BIRD'S NEST.

Two bald eagles in their large nest.
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Bald eagles build enormous nests high in the treetops. The male and female work on the nest together, and this quality time helps them cement their lifelong bond. Their cozy nurseries consist of a framework of sticks lined with softer stuff such as grass and feathers. If the nest serves them well during the breeding season, they'll keep using it year after year. And, like all homeowners, they can't resist the thought of renovating and adding to their abode. Every year, they'll spruce it up with a whopping foot or two of new material.

On average, bald eagle nests are 2-4 feet deep and 4-5 feet wide. But one pair of eagles near St. Petersburg, Florida, earned the Guinness World Record for largest bird’s nest: 20 feet deep and 9.5 feet wide. The nest weighed over two tons.

7. FEMALES ARE LARGER THAN MALES.

Two bald eagles in their large nest.
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In many animal species, males are (on average) larger than females. Male gorillas, for example, dwarf their female counterparts. But for most birds of prey, it's the opposite. Male bald eagles weigh about 25 percent less than females.

Scientists aren't sure why there's such a size difference. One reason might be the way they divide up their nesting duties. Females take the lead in arranging the nesting material, so being bigger might help them take charge. Also, they spend longer incubating the eggs than males, so their size could intimidate would-be egg thieves.

If you're trying to tell male and female eagles apart, this size difference may help you—especially since both sexes have the same plumage patterns.

8. TO IDENTIFY THEM, LOOK AT THE WINGS.

A bald eagle flies across the water.
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People often get excited about a big soaring bird and yell "It's an eagle!” just before it swoops closer and … oops, it's a vulture. Here's a handy identification tip. Bald eagles usually soar with their wings almost flat. On the other hand, the turkey vulture—another dark, soaring bird—holds its wings up in a shallow V shape called a dihedral. A lot of large hawks also soar with slightly raised wings.

9. THEY'RE COMEBACK KIDS.

Baby eagle chicks in a nest.
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Before European settlers arrived, bald eagles were abundant across the U.S. But with settlement came habitat destruction, and the settlers viewed the eagles as competition for game and as a threat to livestock. So many eagles were killed that in 1940 Congress passed an act to protect the birds.

Unfortunately, another threat rose up at about that time. Starting after World War II, farmers and public health officials used an insecticide called DDT. The chemical worked well to eradicate mosquitos and agricultural pests—but as it traveled up the food chain, it began to heavily affect birds of prey. DDT made eagle eggshells too thin and caused the eggs to break. A 1963 survey found just 471 bald eagle pairs in the lower 48 states.

DDT was banned in the early 1970s, and conservationists began to breed bald eagles in captivity and reintroduce them in places across America. Luckily, this species made a spectacular recovery. Now the lower 48 states boast over 9700 nesting pairs.

10. THEY'RE UNIQUELY NORTH AMERICAN.

An African fish eagle flies over the water.
The African fish eagle is a relative of the North American bald eagle.
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You've probably heard of America's other eagle: the golden eagle. This bird lives throughout much of the northern hemisphere. But the bald eagle is only found in North America. It lives across much of Canada and the U.S., as well as northern parts of Mexico.

Though it may be North American, the bald eagle has seven close relatives that are found throughout the world. They all belong to the genus Haliaeetus, which comes—pretty unimaginatively—from the Latin words for "sea" and "eagle." One relative, the African fish eagle, is a powerful symbol in its own right. It represents several countries; for example, it's the national symbol of Zambia, and graces the South Sudanese, Malawian, and Namibian coats of arms.

11. THEY'RE AERIAL DAREDEVILS.

A bald eagle carries a fish off in its talons.
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It seems too weird to be true: While flying, bald eagles sometimes grab each other's feet and spin while plummeting to the earth. Scientists aren't sure why they do this—perhaps it's a courtship ritual or a territorial battle. Usually, the pair will separate before hitting the ground (as seen in this remarkable set of photographs). But sometimes they hold tight and don't let go. These two male bald eagles locked talons and hit the ground with their feet still connected. One subsequently escaped and the other was treated for talon wounds.

12. THEIR EYES ARE AMAZING.

Close-up of a bald eagle's face.
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What if you could close your eyes and still see? Besides the usual pair of eyelids, bald eagles have a see-through eyelid called a nictitating membrane. They can close this membrane to protect their eyes while their main eyelids remain open. The membrane also helps moisten and clean their eyes.

Eagles also have sharper vision than people, and their field of vision is wider. Plus, they can see ultraviolet light. Both of those things mean the expression "eagle eye" is spot-on.

13. THEY MIGRATE … SORT OF.

A bald eagle sits in a snowy tree.
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If you're a bald eagle that nests in northern Canada, you'll probably head south for the winter to avoid the punishing cold. Many eagles fly south for the winter and return north for the summer—as do plenty of other bird species (and retired Canadians). But not all bald eagles migrate. Some of them, including individuals in New England and Canada's Maritime provinces, stick around all year. Whether or not a bird migrates depends on how old it is and how much food is available.

14. THEY CAN SWIM … SORT OF.

A bald eagle
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There are several videos online—like the one above—that show a bald eagle swimming in the sea, rowing itself to shore with its huge wings. Eagles have hollow bones and fluffy down, so they can float pretty well. But why swim instead of soar? Sometimes, an eagle will swoop down and grab an especially weighty fish, then paddle it to shore to eat.

Note that the announcer in the video above says that the eagle's talons are "locked" on a fish that's too heavy to carry. In fact, those lockable talons are an urban legend.

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How Bats Protect Rare Books at This Portuguese Library
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Visit the Joanina Library at the University of Coimbra in Portugal at night and you might think the building has a bat problem. It's true that common pipistrelle bats live there, occupying the space behind the bookshelves by day and swooping beneath the arched ceilings and in and out of windows once the sun goes down, but they're not a problem. As Smithsonian reports, the bats play a vital role in preserving the institution's manuscripts, so librarians are in no hurry to get rid of them.

The bats that live in the library don't damage the books and, because they're nocturnal, they usually don't bother the human guests. The much bigger danger to the collection is the insect population. Many bug species are known to gnaw on paper, which could be disastrous for the library's rare items that date from before the 19th century. The bats act as a natural form of pest control: At night, they feast on the insects that would otherwise feast on library books.

The Joanina Library is famous for being one of the most architecturally stunning libraries on earth. It was constructed before 1725, but when exactly the bats arrived is unknown. Librarians can say for sure they've been flapping around the halls since at least the 1800s.

Though bats have no reason to go after the materials, there is one threat they pose to the interior: falling feces. Librarians protect against this by covering their 18th-century tables with fabric made from animal skin at night and cleaning the floors of guano every morning.

[h/t Smithsonian]

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