Экология сегодня. Макеева М.Н - 4 стр.

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LESSON 1
Grammar:
1. Имя существительное (The Noun). Число (Number). Падеж (Ca-se). Имя существительное в функ-
ции определения.
2. Артикли (Articles).
Text:
ON THE MOVE
As winter approaches, billions of birds worldwide are flying mostly south from their northern homes for
where food is plentiful and living conditions are hospitable. Like clockwork, these birds depart for their winter
homes as a means of survival, despite the fact that their journeys can be quite formidable.
Migrating birds depend on the seasonal availability of resources in order to survive and maintain their
health. In Russia, for example, the Russian Arctic offers swans an abundance of food in the summer, which can
be gathered with less competition from other species, and safe nesting places where there is relative freedom
from human disturbance.
After summer, as the food supply disappears and the ice begins to permeate the region, the birds migrate to
milder climates such as Great Britain where they can find ample resources and shelter to sustain them.
Migration is one of the most widely studied areas of bird biology, and yet it is very poorly understood.
Even though people have observed and noted migrations for centuries, there is sparse information and few
theories about how birds accomplish such impressive flights each year. However, what is becoming clearer is
that these migratory birds are harbingers of the health of our planet, providing clues to changes in the Earth’s
systems that affect the human condition and overall public health.
Many animals migrate, including whales, fish, butterflies, turtles and numerous species of antelope (i.e.
wildebeest, caribou). Moreover, while many of these animals travel incredible distances, like the gray whale,
which travels 10 – 14,000 miles round trip, no animal travels as far and through as much adversity as many bird
species.
In fact, the Arctic Tern accomplishes the extraordinary task of flying from the North Pole to the South Pole
– and back again – each year in a route covering about 22,000 miles! And while migration patterns in North
America are generally north and south, in Europe, a number of migrations occur more east west.
So why do these species go through so much effort and peril. For these birds, it is all about survival, and
their survival depends on the state and conditions of the natural world. Just as they have habitats on which they
depend in one region, they equally depend on habitat in another place that range anywhere from 300 miles to
10,000 miles apart. They begin to migrate when their "biological clock", which is determined by the length of
the day, tells them it is time to go. But other environmental factors such as the weather, their state of nutritional
health and their interaction with other birds enable them to pinpoint exactly when their migration should begin.
Although birds can ride out extreme weather conditions and threats from natural predators, their greatest
threat comes from loss of habitat, mainly due to human development and related activities. Forests and wet-
lands are vital to birds’ survival because they provide food and water, shelter, protection from predators and
places for rest and food during their migrations. Over the past 100 years, as human populations surged and in-
dustrial and technological progress was made, much of the forests and wetlands have been depleted and thus
seriously changed the landscape and resources for these migrating birds. As a result, bird numbers have been
seriously affected in many parts of the world.
Of the 9,600 known bird species, nearly 1,200 are threatened with extinction. About 99 % of the globally
threatened birds are at risk from human activities such as agriculture, logging, and other major changes in the
world’s ecosystems. Hunting and trapping are also contributors, but pale in comparison to changes brought
upon the ecosystems. These ecosystems provide vital services (such as maintaining global climate patterns, me-
diating the carbon cycle, safeguarding watersheds and stabilizing soils), valued at $33 trillion per year. The po-
tential loss of large numbers of species facing extinction is a powerful indication that the quality of these eco-
system services is deteriorating.
In North America, for example, bird observers have seen a steady decline in the numbers of many of the
birds, which migrate to Central and South America. And though deforestation or problems with their summer
breeding habitats were suspected to be the problems, they also realized that forests were not being lost as fast as
the rate of the disappearance of the birds.

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