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species of feathered dinosaurs in China, dating from between 145 and 125 million years ago, is new evidence for the dinosaur-to-bird theory.

After Arechaeopteryx, birds diversified rapidly. Some of the early Cretaceous birds would look quite strange to us, with their toothed beaks and clawed fingers. Since 1990, many new bird fossils have been discovered, adding to our knowledge of this period. Most of the bird lineages of the Cretaceous period died out, but some of them survived to become ancestors of the birds we see today.

Flight gave birds a tremendous advantage, allowing them access to more food supplies and keep away from predators. They had increased freedom to range and migrate, and adapted to an amazing variety of habitats. The Emperor Penguin is better adapted to cold than any other animal on earth. Its short feathers are made up of tiny filaments trat trap the air so effectively that it can survive the Antarctic ice-cap winter. Penguins' wings have evolved to do their "flying" in the water instead of in the air. The ivory gull is able to live in the Arctic all year around, even in the dark winter. The bar-headed goose breeds high up on the Tibetan plateau, the gray gull lives in temperatures up to 50C in the grey sand Atacama Desert in South America, the oilbird lives in the blackness of Venezuelan caves, and the fragile rufous hummingbird survives and breeds at altitudes of 9000 feet. The wrybill in the New Zealand Alps has a beak that is bent to the right, allowing it to probe for larvae under boulders.

The greatest threat to birds comes from man, who hunts, ravages the habitats of wildlife, and introduces alien species, currently threatening almost 1,000 species of birds world-wide. The passenger pigeon, once two billion strong, is now extinct, as is the dodo of Mauritius. Birds on isolated islands are particularly vulnerable, because many of them became flightless in the absence of predators, and were easy pickings for man and his companion animals. Even human efforts to protect wild birds can be counter-productive by encouraging the devastation of the habitat by overpopulation, as in the case of La Perouse Bay in the Canadian Arctic, a former breeding ground for the lesser snow goose.

The birds that survive best are those who are most tolerant of man and most able to take advantage of him. A flock of tiny waxwings can wipe out a blueberry crop within a few days. Some birds, such as the famous Trafalgar park pigeons, have become city dwellers.

Despite the extinction of many species, and the ongoing pressures birds face, they are likely to endure because they have demonstrated their ability to adapt and thrive in the most unlikely conditions.

Sources and resources:
http://www.pbs.org/l ifeofbirds/evolution/index.htm l
An excellent account by PBS.

http://www.pbs.org/wgbh/ev olution/library/03/4/l_034_01. html
More from PBS

http://www.bsu.edu/web/00cy fisher/
Ball State University site

Learn more about this author, Christine G..
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