Warming pushes bushed birds to migrate farther

Yahoo News 14 Apr 09;

PARIS (AFP) – Climate change will force bone-weary birds migrating to Europe from Africa to log extra mileage, with possibly devastating consequences, according to a study released Wednesday.

The annual voyage of some species, which fly north in search of food and suitable climes, could increase by as much as 400 kilometres (250 miles), the research found.

"Marathon migrations for some birds are set to become even longer," said Stephen Willis, a professor at Durham University in Britain and the main architect of the study.

"This is bad news for birds like the Whitethroat, a common farmland bird. The added distance is a considerable threat.

"As temperatures rise and habitats change, birds will face their biggest challenge since the Pleistocene era," which ended 11,000 years ago, he said in a statement.

Some 500 million birds migrate each year from Africa, some weighing as little as nine grammes (three-tenths of an ounce).

To complete a voyage that can be thousands of kilometres (miles) long, birds have to fatten themselves up to twice their normal weight. Some even shrink their internal organs to become more fuel efficient, so any additional distance travelled takes its toll.

"These tiny birds make amazing journeys, pushing themselves to the limits of endurance. Anything that makes those journeys longer ... could mean the difference between life and death," said co-author Rhys Green of Cambridge University.

The study, published in the Journal of Biogeography, looked at the current migration patterns of European Sylvia warblers, a group of birds common in Europe.

Using simulation models, the scientists predict that breeding ranges will shift further northward over the 21st century, while wintering ranges will remain constant for most species.

From 2071 to 2100, nine out of 17 species examined are projected to face longer migrations, particularly birds that cross the Sahara desert, the study found.

Some birds traverse the Sahara and the Mediterranean Sea in a one go, while others make a pit-stop in northern Africa before crossing. Many fly at night, when temperatures are cooler.

A few -- such as the Blackcap -- have started to adapt by spending winters in Britain, but such behaviour remains exceptional, the study said.

"The projected distances for migration would require long- and short-distance fliers to increase their fuel loads by nine percent and five percent of lean body mass respectively," said Nathalie Doswald, a Durham graduate student who worked on the study.

The study forecast that the migration distance of the Orphean Warbler will jump from 2,700 kilometres (1,700 miles) to between 3,050 and 3,350 kilometres (1,900 and 2100 miles), with even longer increases for the Subalpine and Barred Warblers.

Birds face longer migrations due to climate change
Alister Doyle, Reuter 14 Apr 09;

OSLO (Reuters) - Some European birds will have to fly further as global warming shifts their breeding grounds northwards in the biggest challenge to the tiny migrants since the Ice Age, scientists said on Wednesday.

Some types of warbler would have to add 400 kms (250 miles) to twice-yearly trips up to 6,000 kms to and from Africa, according to the report which said it was 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 told Reuters of the study he led with a team of British-based scientists.

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 9 grams (0.3 ounces).

Nine of 17 warbler species studied would have to fly further under projected warming by 2071-2100, especially the whitethroat, the barred warbler or the Orphean warbler that 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 northwards 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.

STOPOVERS

The report, which also involved experts from Cambridge University and the Royal Society for the Protection of Birds, said the European Union should review protected areas for migrant species that need stopovers on their marathon flights.

Still, Willis said migratory birds had proved adaptable before -- surviving Ice Ages and the drying out of the once greener Sahara region about 6,000 years ago.

Willis said the scientists picked warblers because of their widely differing strategies.

Cyprus warblers, for instance, stay on the Mediterranean island year round and would be among those unaffected.

(Reporting by Alister Doyle; Editing by Sophie Hares)