Sunday, 1 May 2011

Report Text_Birds

Early Birds

Archaeopteryx was the first bird to evolve.  Archaeopteryx had wings and feathers but also had teeth and claws – features modern birds do not have.  Scientists believe archaeopteryx probably ran and hopped more than it flew.
©J.Tucciarone (illustration)
Birds are believed to have evolvedfrom meat-eating dinosaurs that walked on their hind legs about 150 million years ago.  Some of these prehistoric creatures had feathers and wings and could fly.  Some had features that were very different from those of modern birds. One of the first birds, called archaeopteryx (ar-key-OP-ter-iks), had teeth in its beak and claws on its wings. It probably ran and hopped instead of flying. As birds continued to evolve, their teeth and claws disappeared. Modern birds do not have teeth or claws.

Coming Out of Their Shells

Birds begin life as eggs.  Most birds lay their eggs in a nest.Incubation time varies for each species. Baby birds cannot fly immediately after hatching. Many species do not have feathers as newborns. However, the babies of species that spend a lot of time on the ground - ducks, chickens, and ratites - are covered in fuzzy feathers and can run or swim almost immediately.   

Several Sets of Feathers

Young birds grow special juvenile feathers before they grow their adult feathers.  Often, a young bird will go through several sets of feathers before it is an adult.  Even adult birds molt, that is, they lose old feathers and replace them with new ones.  Some birds do not become adults for several years while others become adults in a matter of months. 
A kiwi is a small flightless bird that lives in New Zealand.  This amazing bird lays a very large egg, given its body size.  A 1,800g kiwi can lay a 450g egg.  That’s a big baby!  Here you can see how much space the egg takes up when it’s inside the kiwi.
©Otorohanga Zoological Society

Spreading Their Wings

An adult bird no longer depends on its parents. It is ready to look for a mate and sometimes a territory of its own.  Some birds, like swans, mate for life. Others may have many mates throughout their lives.  Birds like parrots and their relatives may live very long lives, between 40-100 years.  Other bird species live shorter lives.  These birds often have more chicks than birds that live longer.

Bird Bodies

Feathers are the one characteristic that all birds share.
Click on the bird picture below to find out more.

Adapted for Just About Anywhere

Bird adaptations are often linked to the environment they live in.  Vultures are a type of bird called a scavenger. Vultures are not fussy eaters and will eat many kinds of carrion. Other birds, like the finch species that live in the Galapagos Islands, have specific niches. They do not directly compete with the other finch species.  Some eat seeds, while others eat insects.

No Teeth, No Problem!

Since birds have no teeth, they must break or tear their food and then swallow the pieces.  The food is first “chewed up” in a special organ called the gizzard.  Birds sometimes swallow tiny stones. The stones remain in the gizzard and help grind the food.  The ground-up food then travels to the stomach to be digested. In many birds, the food is first stored in a pouch called a “crop” part way between the throat and stomach.  This helps birds swallow a lot of food fast so they can fly to a safer place to digest it.

Flying is a Great Way to Travel

Many birds migrate or travel to a warmer climate during the cold winter months.  Birds like geese and ducks migrate in large groups called flocks. Each night the whole group stops to eat and sleep.
There are many bird species thatmigrate to a new environment during parts of the year. These migrations may cover relatively short distances or very great distances.  Most migrating bird species move to cooler climates in summer. During this time, they reproduce. They migrate to warmer climates in the winter.  Arctic terns have the longest migration. They migrate from the Arctic to the Antarctic and back every year.  That’s more than 32,000 km!  Scientists are still trying to discover exactly how migrating birds know where to go every year. 

Not All Birds Fly

All birds have wings and feathers, but not all birds fly. Penguins, for example, cannot fly, but they are excellent swimmers. They have special oily feathers that make them waterproof. Ostriches and emus are two land birds that do not fly. They use their long legs to speed away from predators.
Most bird species that cannot fly are found on islands. Scientists think that over time these birds lost the ability to fly because they no longer needed to fly away to find food or escape from predators.  Many of these island birds are now endangered. They now have predators such as cats and rats. These animals arrived with people and now attack the flightless birds and their nests.

Giving Plants a Lift

Birds fill many important roles in their environments. Birds and plants are connected in many ways.  Hummingbirds, honeycreepers, and sunbirds have long beaks specially adapted for reaching deep inside flowers.  As they search for sweet flower nectar, they help pollinateflowers and other plants. 
Many birds are responsible for transporting seeds from one place to another. A few even play a role in helping the seeds germinate and grow.  In the tropics, toucans, hornbills, and parrots open and eat many kinds of fruits.  As the birds fly off with the fruit, the seeds are scattered to new locations. This helps new trees grow far from the parent tree.
Did You Know?©

Dancers and Decorators

Many birds have special or unusual behaviors. Often these behaviors are part of the mating ritual.  The male bowerbirds of Australia make elaborate structures out of brightly colored objects they have collected and arranged. They do this to get females to mate with them. Some birds do a special dance. The blue-footed boobies of the Galapagos Islands wave their big blue feet to attract a mate. 
Bowerbird males make very fancy structures to attract females.  Some collect things that are a certain color or that are shiny.
The cuckoo bird lays its eggs in other birds’ nests so that it doesn’t have to use energy raising chicks.  The unknowing parent of the other bird species feeds and cares for the baby cuckoos even though they do not belong in the nest.

Feathers, Food, and Beautiful Songs

People use birds for many things.  Their feathers are used for decoration and for making warm clothing and pillows.  People all over the world eat different birds. People hunt wild birds such as pheasants and grouse.  Chickens, ducks, and ostriches are some of the birds that are raised for food and feathers.
People rely on birds for many things. Birds such as pigeons, chickens, and ducks provide food for people. Some people keep birds as pets. Others enjoy bird watching out in the wild.  Birds in some cultures are even thought to signal when earthquakes are coming. Birds also are very important in maintaining environmental balance. Decreases in the bird population serve as signals that problems like pollution and loss of habitat are changing the world we live in.  

Bird Conservation

Many bird species are endangered as a result of human activities. For example, people hunted the giant moa, which stood 3.7 m tall, toextinction. Peregrine falcons almost became extinct because of thepesticide DDT.  This pesticide entered the food chain and eventually ended up in the bodies of the falcons.  It caused their eggs’ shells to be thin and brittle. Because of this, many eggs broke before it was time for the chicks to hatch.  A ban on DDT, captive breeding programs, and habitat conservation have helped peregrine falcons around the world make a successful recovery.Birds

Our Feathered Friends

Earth is home to more than 9,000 different species of birds. Birds arewarm-blooded, feathered animals of many shapes, sizes, and colors. Some birds live in large groups called flocks. They spend their entire lives with lots of other birds. Other species are solitary. They rarely interact with members of their species. Most birds can fly, and they rank as the most skilled fliers in the animal kingdom. Being warm-blooded has helped birds adapt and spread to many kinds of environments. Today, birds are found on every continent on Earth - even Antarctica where penguins live happily in temperatures that drop as low as -35°C.

1 comment:

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