Sunday, 1 May 2011

Report Text_Eagles @Globio.org

Eagles

Big Birds

Eagles belong to a group of birds called raptors. They are amazing, powerful predators with sharp eyesight, light bodies, and soaring wings. Eagles use their dagger beaks and sharp talons to hunt fish, snakes, frogs, other birds, and small mammals. They are some of the world’s largest birds of prey.
There are 59 different kinds of eagles on Earth and they live in everyenvironment except the polar regions of Antarctica. The majority of the world’s eagles soar in the skies over Asia, Russia, and Europe. Two species live in North America and two in South America.
The tawny eagle is a kind of soaring eagle. It hunts small animals but mostly eats other predator’s catches or animals that have died naturally. As long as the kill is fresh the tawny eagle will eat it.

Giants of the Treetops and Smallish Snake Hunters

The harpy eagle is a fierce hunter. They can quickly fly through the tropical rainforest and snatch a sloth right off of a tree with its enormous talons.
The harpy eagle is a fierce hunter. They can quickly fly through the tropical rainforest and snatch a sloth right off of a tree with its enormous talons.
©S.Holt/GLOBIO.org
Scientists organize eagles into four main groups: harpy eagles, serpent or snake eagles, booted eagles and fish or sea eagles. Two of the largest eagles are the Philippine eagle and the harpy eagle of tropical South America. Each can weigh more than 9 kg and have wings that spread 2 m. Using their huge talons, these giants of the treetops can kill and carry off prey as large as monkeys.
Most eagles are large powerful hunters. However, some are just small pigeon-sized birds that fly only short distances, eating insects and even fruit! The crested serpent eagle is the size of a small chicken. It spends its days walking and climbing through its African forest home, searching for snakes. Another smallish eagle, the African vulturine fish eagle, is nearly an herbivore. It feeds mainly on oily palm nuts.

Sharpest Eyes in the Skies

Most eagles spend their time soaring on air currents over fields, forests, mountain ridges, or coast lines looking for food. Like all birds, eagles see in color. Their vision at night is poor, but during the day all eagles have very sharp eyesight--four to five times stronger than a human with perfect vision. They can spot movement long distances away. An eagle can easily see a rabbit on the ground from 300 m up and 1 km away! In order to blink, eagles have a clear, inner eyelid called a nictitating membrane.
Eagle’s eyes are almost as big as human eyes but their heads are much smaller. They can see much better than us and have color vision.
Eagle’s eyes are almost as big as human eyes but their heads are much smaller. They can see much better than us and have color vision.
©S.Gettle/GLOBIO.org
Why do eagles have such sharp eyesight? Part of the reason is that eagles have TWO focus areas in each eye!  Humans have just one. Eagles have binocular vision to see forward, the way you do. At the same time an eagle can see out the side or slightly backwards, which is called monocular vision. The two types of vision combined help the eagle see small objects far away.

The Wing’s the Thing

A pair of little eagles flying together. The eagle on the left is a female and the other is the male. Can you tell the difference between the male and female?
A pair of little eagles flying together. The eagle on the left is a female and the other is the male. Can you tell the difference between the male and female?
©Julian Robinson
Eagles that live in forests, such as the crested serpent eagle, have short wings and long tails. These features enable them to twist and turn easily in the air, an advantage when chasing prey at high speed through tree trunks and branches. Soaring eagles, such as the golden eagle and Africa's bateleur eagle, have long wings and short tails. These features let them glide effortlessly on rising air currents. However, these same features make soaring eagles poor flyers, so every takeoff and landing is an adventure! As a result, soaring eagles often hunt from high perches, where they can literally "fall" into the air and swoop down on unsuspecting fish and mammals.

Feet that Fit the Food

Eagles look similar around the world. They have the same shape, sharp talons, dagger beak, and keen eyesight. However, each species hunts its home landscape with special skills.  An eagle’s wings and tail might determine where and how an eagle flies, but its feet tell you what kind of hunter it is.
Look at the size of this 7-month-old harpy eagle’s talons!
Look at the size of this 7-month-old harpy eagle’s talons!
©P.Oxford/Foto Natura/Minden Pictures
Harpy Eagles
These six types of eagles are forest-dwelling giants that prey on such large mammals as deer and monkeys, using the huge, powerful, hooked talons on their feet.
Serpent eagle’s gripping feet are perfect for hunting snakes but also great for perching on branches.
Serpent eagle’s gripping feet are perfect for hunting snakes but also great for perching on branches.
©P.Oxford/Minden Pictures
Serpent or Snake Eagles
There are 12 species of serpent eagles, also called snake eagles. They perch on high trees and swoop to capture snakes, frogs, and lizards, even the poisonous ones! These eagles have gripping feet with needle-like talons and long legs. The lower section of their legs is not feathered. Instead it is covered by armor-like scales that help protect against snakebites.
This young golden eagle is now old enough to live away from the nest and find its own food.
This young golden eagle is now old enough to live away from the nest and find its own food.
©S.Gettle/GLOBIO.org
Booted Eagles
The 30 species of booted eagles have feathers growing down their legs and covering their toes. This group includes the golden eagle, which is found around the world and has learned to hunt and eat almost anything it can catch. Golden eagles eat rabbits, snakes, squirrels, other birds, even small dogs. In Greece, they even eat turtles, soaring high then crashing them onto the ground to crack open their shells.
An African fish eagle searches for its next meal.
An African fish eagle searches for its next meal.
©G.Ellis/GLOBIO.org
Fish or Sea Eagles
Sea eagles’ oily-feathered bodies are perfectly adapted to the life of a fish hunter. The 11 sea eagles, which include America's beloved bald eagle, tend to specialize in eating fish and water birds. Feet with spiny pads, curved claws, and an outer toe help them catch and hold fish. Some even hunt flamingoes and poisonous sea snakes.

Big Babies in Big Nests

Wedge-tailed eagle males hunt for food for their chicks until they are about 30 days old and then both parents share responsibility for hunting for meals.
Wedge-tailed eagle males hunt for food for their chicks until they are about 30 days old and then both parents share responsibility for hunting for meals.
©Julian Robinson
Each year a pair of eagles may have one or two eggs, laid in a nest generally made of sticks. Large eagles such as the bald eagle of North America build nests over 1 min diameter. Many eagles return to the same nests and continue to add sticks and branches. Some nests, such as those of the golden eagle, grow as big as a car!  A nest like this can be 100 years old and used by many eagle pairs over time. 
Eagles make some of the most attentive and caring parents of all birds. Eagle babies, called chicks or eaglets, take longer than most birds to develop and learn to fly. A golden eagle chick remains in its nest for over 3 months before it tries to fly.

A Perfect Eagle Environment

Before a bald eagle can build a nest it must choose a location. Nests are usually built in forests near bodies of water so they can easily fish for a meal. Humans can create problems for eagles so they don’t usually live close to people.
Before a bald eagle can build a nest it must choose a location. Nests are usually built in forests near bodies of water so they can easily fish for a meal. Humans can create problems for eagles so they don’t usually live close to people.
©G.Ellis/GLOBIO.org
Two things make a perfect environment for eagles: food to hunt and high places to build nests and raise eaglets safely. Since eagles can soar great distances searching for prey, their homes may cross over more than one type of environment. For example, members of the sea eagle group may hunt over the water, along the shore, or in forests and rivers.

Moving On

In some cases, eagles can move from one environment to another when the season becomes too cold or hot.  While migrating, eagles such as the bald eagle ride columns of rising air and can average speeds of 50 kph. Bald eagles usually migrate in groups called a “stream.”  Each stream can be 40-50 kmlong, with birds spread out about 1 km apart. Scientists are still trying to understand exactly how eagles know the migration route and what clues they use to navigate long distances across the earth.

High-Level Hazard

Wind farms can be a threat to eagles because the blades spin so fast that they can’t see the danger. They are sometimes attracted to the wind farms because the strong winds can give them a lift when soaring.
Habitat loss can disrupt the entire food chain in an area. Eagles are at the top of their food chains, so if their food disappears they have to find somewhere else to hunt, build their nests, and raise their chicks.
©G.Ellis/GLOBIO.org
If you are the best aerial hunter in your environment, and most eagles are, you sit at the top of the food chain. Being king of the sky can be great, but it can also be dangerous. At the peak of the food chain, all the chemicals and pollution in the environment add up and can be in the food you eat and feed your babies. This can make eagles very sick or unable to have healthy chicks. Poaching is also a threat to eagles all over the world, although, most eagles are protected by special laws and regulations.

Discovery of a Lifetime: A Lost Eagle

On November 3, 1993, American scientist Russell Thorstrom was walking through the tropical forests of Madagascar when he spotted one of the six rarest birds in the world. It was a Madagascar serpent eagle, a species that hadn't been seen in 60 years! However, the nation of 14 million people, who are known as Malagasys, is very poor. In their struggle to survive, the Malagasys have logged and cleared much of their nation's forest, destroying a critical habitat for the serpent eagle.
When Thorstrom and other biologists returned to the site a few weeks later, they found nearby forests being burned by local farmers—and no sign of the eagle. However, more recently researchers have discovered 15 eagles at nine locations. In 2006 they discovered the first Madagascar serpent eagle nest.

Eagles Inspire Imagination

This mask is made with an eagle skull and feathers. The Kwakiutal people of Canada use transformation masks to tell stories and about their culture and history.
This mask is made with an eagle skull and feathers. The Kwakiutal people of Canada use transformation masks to tell stories and about their culture and history.
©F.Lanting/Foto Natura/Minden Pictures
For centuries, people all around the globe have admired eagles so much that they attributed great powers to the birds. Eagles’ powerful hooked beaks and sharp talons adorned the flags that led ancient Roman armies into battle. According to stories In South America, the spot on which an eagle landed dictated where the ancient Aztecsshould build a city. Today, professional football (soccer) teams in Portugal, Italy, Greece, Turkey, and Spain have eagle mascots on their uniforms to symbolize strength and dominance.
Many cultures gathered or even hunted eagles for their beautiful and "powerful" feathers. Until recently, most cultures believed it was evil or bad luck to kill or injure an eagle. Eagles are now protected in many areas and can be seen hunting and nesting in the wild and even sometimes in cities!

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