explain the whole lifestyle of birds
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Answer:
The life of birds has changed enormously since man spread widely around the planet, and began to develop and despoil it. Man is the primary force threatening the natural world. Habitat destruction, , hunting, introduction of alien species and pollution combine to threaten almost 1000 species of birds world-wide.
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Explanation:
Answer:
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Explanation:
No bird gives birth to live young. Birds quickly form and lay an egg covered in a protective shell that is then incubated outside the body.
Birds developed much great mobility than a mammal, but at the cost of being unable to carry its growing offspring about in its body. Unlike, say, a dog carrying a litter of puppies.
The large size of a egg makes it difficult for the female to retain more than a single one egg at a time - carrying eggs would make flying harder and require more energy. (Bird eggs vary in size from the tiny 0.2 gramme eggs of hummingbirds to the enormous 9 kilogram eggs of the extinct elephant bird.)
Just as an aircraft cannot fly if it is overweight, all female birds must dispense with the fertile egg as soon as it is formed. And because the egg is such a protein-rich high-nuitrition prize to all sorts of predators, birds must find a secure place to hatch their eggs. Although birds' eggs appear to be fragile, they are in fact extremely robust. The oval shape applies the same rules of engineering as an arched bridge; the convex surface can withstand considerable pressure without breaking. This is essential if the egg is not to crack under the weight of the sitting bird. It takes 26 pounds of pressure to break a swan's egg and 120 pounds to smash the egg of an ostrich.
Finding a place to safely place and hatch their eggs, and raise their young to the point of independence, is a challenge birds have solved in many clever ways. They use artistry, intricate design and complex engineering. The diversity of nest architecture has no equal in the animal kingdom.
In many species the male bird's skill at nest building is a sign of his suitability as a mate; he invests huge effort in the task. Males of the European house wren build up to 12 nests to attract females. They will continue to build new nests until a female is happy with the construction.