全球變暖 候鳥被迫遷徙更遠

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 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 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 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.

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 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 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

本週三公佈的一項研究顯示，氣候變化將迫使從非洲遷徙至歐洲的候鳥再多飛數百英里，對於已經精疲力盡的鳥來說，這可能會帶來毀滅性的後果。

研究發現，一些向北飛行以覓食和尋找合適棲息地的候鳥每年飛行的距離可增加約400公里（合250英里）。

英國達翰姆大學的教授、研究骨幹斯蒂芬•威利斯說：“對於一些候鳥來說，馬拉松式的遷徙路程將變得更遠。”

“這對白喉鶯這樣的普通農田鳥類來說是個壞消息，多飛的行程對於它們來說是個很大的威脅。”

他在一份聲明中稱：“隨着溫度上升，棲息地環境變化，候鳥將面臨自1.1萬年前結束的更新世（譯者注：屬於或標誌第四紀的兩個時期中較早時代的地質時期、岩石系列和沉積礦牀的，這一時期以互生外貌、北方冰蝕退縮和人類祖先的出現爲特徵）時期以來最大的挑戰。”

每年約有五億隻候鳥從非洲向北遷徙，一些候鳥體重僅爲9克（合0.3盎司）。

爲飛完長達數千公里的行程，候鳥需將體重增至正常水平的兩倍，有些候鳥甚至收縮內臟以減少消耗，因此任何額外的行程都會造成傷害。

這項在《生物地理學雜誌》上發表的研究結果顯示，在2071至2100年間，所研究的17種鳥類中有9種將面臨更長的遷徙行程，尤其是需要飛越撒哈拉沙漠的鳥類。

有些候鳥一口氣橫穿撒哈拉沙漠和地中海，而有些則在穿越前在北非稍作休整。很多鳥類在溫度較低的夜間飛行。

研究稱，少數鳥類如黑頂鶯等已經開始適應在英國過冬，但這種情況還只是少數。

研究預測，歌林鶯的遷徙行程將從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）之間，而亞高山林鶯和橫斑林鶯增加的行程則更遠。

Vocabulary:

bone-weary：extremely tired or weary; also called bone-tired（精疲力盡的，極其疲倦的）

traverse：to pass or move over, along, or through.（橫越，橫貫）

in a one go:一口氣

pit-stop：旅行中暫時停下（原指賽車比賽中進站加油、維修的站點）