Climate change will force bone-weary birds migrating to Europe from Africa to log extra mileage¹, with possibly devastating² consequences, according to a study released on 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 migrations⁴ 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 long, birds have to fatten⁵ 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 toll⁶.

The study is published in the Journal of Biogeography. 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 Mediterranean⁷ 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 remains⁸ exceptional, the study said.

The study forecast that the migration³ 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.

本周三公布的一项研究显示，气候变化将迫使从非洲迁徙至欧洲的候鸟再多飞数百英里，对于已经精疲力尽的鸟来说，这可能会带来毁灭性的后果。

研究发现，一些向北飞行以觅食和寻找合适栖息地的候鸟每年飞行的距离可增加约400公里（合250英里）。

英国达翰姆大学的教授、研究骨干斯蒂芬•威利斯说：“对于一些候鸟来说，马拉松式的迁徙路程将变得更远。”

“这对白喉莺这样的普通农田鸟类来说是个坏消息，多飞的行程对于它们来说是个很大的威胁。”

他在一份声明中称：“随着温度上升，栖息地环境变化，候鸟将面临自1.1万年前结束的更新世（译者注：属于或标志第四纪的两个时期中较早时代的地质时期、岩石系列和沉积矿床的，这一时期以互生外貌、北方冰蚀退缩和人类祖先的出现为特征）时期以来最大的挑战。”

每年约有五亿只候鸟从非洲向北迁徙，一些候鸟体重仅为9克（合0.3盎司）。

为飞完长达数千公里的行程，候鸟需将体重增至正常水平的两倍，有些候鸟甚至收缩内脏以减少消耗，因此任何额外的行程都会造成伤害。

这项在《生物地理学杂志》上发表的研究结果显示，在2071至2100年间，所研究的17种鸟类中有9种将面临更长的迁徙行程，尤其是需要飞越撒哈拉沙漠的鸟类。

有些候鸟一口气横穿撒哈拉沙漠和地中海，而有些则在穿越前在北非稍作休整。很多鸟类在温度较低的夜间飞行。

研究称，少数鸟类如黑顶莺等已经开始适应在英国过冬，但这种情况还只是少数。

研究预测，歌林莺的迁徙行程将从2700公里（合1700英里）增加到3050公里至3350公里（合1900英里至2100英里）之间，而亚高山林莺和横斑林莺增加的行程则更远。

Vocabulary:

bone-weary：extremely tired or weary; also called bone-tired（精疲力尽的，极其疲倦的）

traverse：to pass or move over, along, or through.（横越，横贯）

in a one go:一口气

pit-stop：旅行中暂时停下（原指赛车比赛中进站加油、维修的站点）