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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.
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(Agencies)
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本周三公布的一項研究顯示，氣候變化將迫使從非洲遷徙至歐洲的候鳥再多飛數(shù)百英里，對于已經(jīng)精疲力盡的鳥來說，這可能會帶來毀滅性的后果。
研究發(fā)現(xiàn)，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(dá)翰姆大學(xué)的教授、研究骨干斯蒂芬?威利斯說：“對于一些候鳥來說，馬拉松式的遷徙路程將變得更遠(yuǎn)?！?/font>
“這對白喉鶯這樣的普通農(nóng)田鳥類來說是個壞消息，多飛的行程對于它們來說是個很大的威脅?！?/font>
他在一份聲明中稱：“隨著溫度上升，棲息地環(huán)境變化，候鳥將面臨自1.1萬年前結(jié)束的更新世（譯者注：屬于或標(biāo)志第四紀(jì)的兩個時期中較早時代的地質(zhì)時期、巖石系列和沉積礦床的，這一時期以互生外貌、北方冰蝕退縮和人類祖先的出現(xiàn)為特征）時期以來最大的挑戰(zhàn)?！?/font>
每年約有五億只候鳥從非洲向北遷徙，一些候鳥體重僅為9克（合0.3盎司）。
為飛完長達(dá)數(shù)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(nèi)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(xué)雜志》上發(fā)表的研究結(jié)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(shù)鳥類如黑頂鶯等已經(jīng)開始適應(yīng)在英國過冬，但這種情況還只是少數(shù)。
研究預(yù)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(yuǎn)。
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（實習(xí)生許雅寧 英語點津姍姍編輯） |
