In warmer world, longer flights

Some types of warbler would have to add 250 miles to twice-yearly trips of up to 4,000 miles to and from Africa, according to the report, described as the first to examine the potential impact of climate change on avian migration.

"For some birds, the extra distance might make the difference between being able to make it or not," Stephen Willis of Durham University said of the study he led with a team of scientists based in Britain.

The report, adding to projected threats to animals and plants from global warming, said an estimated 500 million birds migrate from Africa to Europe and Asia every year. Some weigh just 0.3 ounces.

Nine of 17 warbler species studied would have to fly farther under projected warming by the latter third of this century. Among those most affected are the whitethroat, the barred warbler, and the Orphean warbler, which cross the Sahara Desert, according to the study in the Journal of Biogeography.

"Some species may be able to adapt and change, for example, by adopting shorter migration routes if they can find enough food at the right time," Willis said in a statement. Some blackcap warblers in Germany had dropped winter flights south.

"As temperatures rise and habitats change, birds will face their biggest challenge since the Pleistocene era," he said.

The end of the last Ice Age 10,000 years ago marked the end of the Pleistocene.

The study said breeding grounds were moving northward because of climate change, while wintering regions nearer the equator were less affected. The Arctic region is warming almost twice as fast as the rest of the globe.

The report, which also involved specialists from Cambridge University, said the European Union should review protected areas for migrant species that need stopovers on their marathon flights.