Winners and Losers; Climate change is shifting the reproductive and migratory patterns of birds and other animals.

Byline: Mac Margolis and Clint Witchalls (With Sarah Sennott in London)

One afternoon a couple of months ago, Ali Cuthbert was strolling through the grounds of the Royal Botanic Gardens in London when she heard a racket overhead. She looked up in the towering oak trees and saw a riot of emerald green parakeets. "I thought I was hallucinating," says Cuthbert, the gardens' public-relations manager. "They're so strange looking." It was no illusion. Oxford University researchers now reckon that some 20,000 wild parrots make their home in clammy England--and that their numbers are rising at the clip of 30 percent a year. Welcome to the British Isles, the newest stop in the tropics.

It's not just England that hasn't been her temperate self lately. A run of wimpy winters and blazing summers--and plenty of weird weather in between--has remade landscapes across the map, drowning China in Biblical rains, cooking vineyards in Alsace. The climate shifts are also changing centuries-old migration and breeding patterns: last week a North American purple martin was sighted for the first time in Scotland, thousands of miles off course. Colonies of stink bugs have chewed their way up from their customarily toasty Mediterranean habitat to London neighborhoods. The iconic edelweiss, a cold-loving mountain evergreen, has been climbing up the Alps at the rate of one to four meters a decade, driven to higher elevations by warmer climes below. Stultifying summers could also explain why the only orioles in Baltimore, Maryland, these days are the kind in flannels and cleats.

What in the name of Noah is going on? Breakneck economic development, population growth and deforestation have for decades wreaked the most havoc on ecosystems. But now scientists are beginning to think that extreme weather brought on by climate change--things like prolonged droughts, unseasonable rains and balmy winters in the temperate zones--are stretching growing seasons, expelling cold-loving plants and animals from their habitats and sending flocks of seabirds off course.

A 0.6 degree ...