Transcript

NARRATOR:

The bar-headed goose - it winters on the plains of Northern India. And each spring it cuts through the Himalayan barrier, threading its way through high glaciated valleys to reach its nesting grounds.

[MUSIC PLAYING]

These geese hold what is surely the altitude record for migrating birds. Many years ago, an astronomer in Northern India was photographing the Moon. When he developed the prints, one showed a skein of geese silhouetted against the Moon's disc. From their size, he calculated that they must have been flying at 29,000 feet. That's almost the height of Everest.

Bar-heads breed in what must be some of the most remote and desolate places on Earth. Most nest on soda lakes on the Tibetan Plateau. But a few travel on north and west to the Tian Shan and Pamir. Some 200 pairs nest on Karakum. Another 50 or so come here, to Lake Rankoo, a shallow salt lake hard by the border with Xianjiang.

[GEESE HONKING]

Almost no rain falls here. And even in winter, there's little snow. The lake's surroundings are a high, dry desert.

The geese arrive in late May, when the lake is still frozen. They settle on barren salty islands. The female digs a hole in the caustic soil, and lines it with down from her breast.

In this simple nest, she lays between two and five eggs. It will take them nearly a month to hatch. She shoulders the burden of all the incubating. But while she sits, her mate stands guard.

Though nesting on islands keeps wolves and foxes at bay, there are other dangers - ravens. When the first clutches hatch, a few addled eggs are left in the abandoned nests. These attract scavengers from the surrounding mountains. But given the chance, ravens take eggs from any unguarded nest.

Most eggs do hatch safely. The chicks remain in the nest for a day. Then their mother calls them down to the water.

[HONKING AND CHEEPING]

Rankoo is very shallow. Much of the lake is only three to six feet deep. In summer, its corrosive waters warm rapidly. And there are prolific hatches of midges, full of protein for the growing goslings.